The PYQ practice room
GATE EC 2022 Set 1
All 65 solved GATE EC 2022 Set 1 questions in exam order. Open a question, commit to an answer, and learn from the step-by-step solution. One question at a time.
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100
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General Aptitude (GA)
101
Q1MCQ1 markEasyMr. X speaks _______ Japanese _______ Chinese.Think it through. Then check your answer.Question
Mr. X speaks _______ Japanese _______ Chinese.Correct answer
(C) neither / nor
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The correct correlative conjunction pair is neither / nor. The pair either / or is also correct, but it is not provided as an option in that order. Therefore, option (C) is the grammatically correct choice.2
Q2MCQ1 markEasyA sum of money is to be distributed among P, Q, R, and S in the proportion , respectively. If R gets ₹ 1000 more than S, what is the share of Q (in ₹)?Think it through. Then check your answer.Question
A sum of money is to be distributed among P, Q, R, and S in the proportion , respectively.If R gets ₹ 1000 more than S, what is the share of Q (in ₹)?Correct answer
(D) 2000
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Let the shares of P, Q, R, and S be , , , and respectively.
Given that R gets ₹ 1000 more than S:
The share of Q is :
Share of .3
Q3MCQ1 markMediumA trapezium has vertices marked as P, Q, R and S (in that order anticlockwise). The side PQ is parallel to side SR. Further, it is given that, ,…Think it through. Then check your answer.Question
A trapezium has vertices marked as P, Q, R and S (in that order anticlockwise). The side PQ is parallel to side SR.Further, it is given that, , , and .What is the shortest distance between PQ and SR (in cm)?Correct answer
(B) 2.40
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Let the trapezium be with . Given , , , and .
Draw a line from parallel to that intersects at point .
Then and .
In , the side .
The sides of are , , and .
Since , is a right-angled triangle with the right angle at .
The shortest distance between and is the height () of the trapezium, which is also the altitude of from vertex to the base .
Area of .
Also, Area .
.4
Q4MCQ1 markMediumThe figure shows a grid formed by a collection of unit squares. The unshaded unit square in the grid represents a hole. What is the maximum number of squares without a "hole in…Think it through. Then check your answer.Question
The figure shows a grid formed by a collection of unit squares. The unshaded unit square in the grid represents a hole. What is the maximum number of squares without a "hole in the interior" that can be formed within the grid using the unit squares as building blocks?Correct answer
(B) 20
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Let the grid be a grid. The unshaded unit square represents a hole. We need to find the maximum number of squares without a "hole in the interior".Assume the hole is at position in a 1-indexed grid.1. squares:There are unit squares in total.
One square contains the hole.
Number of squares without a hole = .2. squares:The number of possible squares in a grid is .
A square contains the hole if its top-left corner is at , , , or . These are 4 squares.
Number of squares without a hole = .3. squares:The number of possible squares in a grid is .
All these 4 squares (top-left corners at , , , ) will contain the hole at .
Number of squares without a hole = .4. squares:There is only possible square.
This square contains the hole.
Number of squares without a hole = .Total maximum number of squares without a "hole in the interior" = .The final answer is5
Q5MCQ1 markMediumAn art gallery engages a security guard to ensure that the items displayed are protected. The diagram below represents the plan of the gallery where the boundary walls are opaque.…Think it through. Then check your answer.Question
An art gallery engages a security guard to ensure that the items displayed are protected. The diagram below represents the plan of the gallery where the boundary walls are opaque. The location the security guard posted is identified such that all the inner space (shaded region in the plan) of the gallery is within the line of sight of the security guard. If the security guard does not move around the posted location and has a view, which one of the following correctly represents the set of ALL possible locations among the locations P, Q, R and S, where the security guard can be posted to watch over the entire inner space of the gallery.
Correct answer
(C) Q and S
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To watch over the entire inner space of the gallery from a single fixed point, that point must have a direct line of sight to every other point in the shaded region. This is equivalent to finding points in the 'kernel' of the polygon.1.Point P: From P, the bottom-right 'wing' of the gallery is partially obscured by the inner reflex vertex (the 'V' shape in the middle). Thus, P cannot see the entire space.2.Point R: Similarly, from R, the bottom-left 'wing' is partially obscured by the inner reflex vertex. Thus, R cannot see the entire space.3.Point Q: Point Q is located centrally such that straight lines can be drawn from it to any point within the shaded region without crossing the boundary walls. It can see the entire space.4.Point S: Point S is located at the bottom tip. From this position, the entire 'V' shaped gallery is visible as it opens up towards the top. There are no obstructions to the line of sight for any part of the interior.Therefore, the set of all possible locations among P, Q, R, and S is {Q, S}.6
Q6MCQ2 marksEasyMosquitoes pose a threat to human health. Controlling mosquitoes using chemicals may have undesired consequences. In Florida, authorities have used genetically modified mosquitoes…Think it through. Then check your answer.Question
Mosquitoes pose a threat to human health. Controlling mosquitoes using chemicals may have undesired consequences. In Florida, authorities have used genetically modified mosquitoes to control the overall mosquito population. It remains to be seen if this novel approach has unforeseen consequences. Which one of the following is the correct logical inference based on the information in the above passage?Correct answer
(D) Using chemicals to kill mosquitoes may have undesired consequences but it is not clear if using genetically modified mosquitoes has any negative consequence
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Let's break down the passage and evaluate each option:Passage Analysis:1."Controlling mosquitoes using chemicals may have undesired consequences."- This indicates a possibility of negative outcomes with chemical control.
- This indicates uncertainty about the consequences of genetically modified mosquitoes. It does not state that there will be unforeseen consequences, nor does it state that there will not be any.
- (A) Using chemicals to kill mosquitoes is better than using genetically modified mosquitoes because genetic engineering is dangerous
- The passage does not state that chemical control is better. It only mentions potential undesired consequences for chemicals. It also does not explicitly state that genetic engineering is dangerous, only that its unforeseen consequences are yet to be seen.
- Therefore, this inference is incorrect.
- (B) Using genetically modified mosquitoes is better than using chemicals to kill mosquitoes because they do not have any side effects
- The passage explicitly states that "It remains to be seen if this novel approach has unforeseen consequences." This directly contradicts the claim that they "do not have any side effects."
- Therefore, this inference is incorrect.
- (C) Both using genetically modified mosquitoes and chemicals have undesired consequences and can be dangerous
- For chemicals, the passage says they "may have undesired consequences." This is a possibility, not a certainty.
- For genetically modified mosquitoes, it says "It remains to be seen if... unforeseen consequences." This means we don't know yet if they have undesired consequences. Stating that they have undesired consequences is a stronger claim than what the passage supports.
- Therefore, this inference is too strong and not fully supported by the passage.
- (D) Using chemicals to kill mosquitoes may have undesired consequences but it is not clear if using genetically modified mosquitoes has any negative consequence
- "Using chemicals to kill mosquitoes may have undesired consequences**" directly matches the first sentence of the passage.
- "but it is **not clear if using genetically modified mosquitoes has any negative consequence**" accurately reflects "It **remains to be seen if this novel approach has unforeseen consequences."
- This option is a precise and logical inference based only on the information provided in the passage.
7
Q7MCQ2 marksEasyConsider the following inequalities. (i) (ii) Which one of the following expressions below satisfies the above two inequalities?Think it through. Then check your answer.Question
Consider the following inequalities.
(i)
(ii) Which one of the following expressions below satisfies the above two inequalities?Correct answer
(C) 4 < x < 5
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To find the values of that satisfy both inequalities, solve them individually:1.From inequality (i):
2.From inequality (ii):
Combining these two results, we get the range . Thus, option (C) is correct.8
Q8MCQ2 marksEasyFour points , , , and represent the vertices of a quadrilateral. What is the area enclosed by the quadrilateral?Think it through. Then check your answer.Question
Four points , , , and represent the vertices of a quadrilateral.What is the area enclosed by the quadrilateral?Correct answer
(C) 8
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The vertices of the quadrilateral are , , , and .1.The diagonal lies on the -axis (since for both points). Its length is .2.The diagonal lies on the horizontal line . Its length is .3.These two diagonals are perpendicular because one is vertical and the other is horizontal. They intersect at the point .The area of a quadrilateral with perpendicular diagonals is given by:Thus, the area is 8 square units.9
Q9MCQ2 marksMediumIn a class of five students and , only one student is known to have copied in the exam. The disciplinary committee has investigated the situation and recorded the…Think it through. Then check your answer.Question
In a class of five students and , only one student is known to have copied in the exam. The disciplinary committee has investigated the situation and recorded the statements from the students as given below.Statement of P: has copied in the exam.
Statement of Q: has copied in the exam.
Statement of R: did not copy in the exam.
Statement of S: Only one of us is telling the truth.
Statement of T: is telling the truth.The investigating team had authentic information that never lies.Based on the information given above, the person who has copied in the exam isCorrect answer
(B) P
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1.We are given that never lies, so 's statement is true.2.'s statement is: "Only one of us is telling the truth."3.Since is telling the truth, and is one of the five students, must be the only person telling the truth. This means and are all lying.4.Analyze the lying statements to find the truth:- Statement of R: " did not copy in the exam." Since is lying, the truth is that did copy in the exam.
- Statement of P: " has copied in the exam." Since is lying, did not copy.
- Statement of Q: " has copied in the exam." Since is lying, did not copy.
- Statement of T: " is telling the truth." Since is lying, is actually lying (which is consistent with our finding).
10
Q10MCQ2 marksMediumConsider the following square with the four corners and the center marked as and respectively. [figure] Let and represent the following operations:…Think it through. Then check your answer.Question
Consider the following square with the four corners and the center marked as and respectively.Let and represent the following operations:: rotation of the square by degree with respect to the axis.
: rotation of the square by degree with respect to the axis.
: rotation of the square by degree clockwise with respect to the axis perpendicular, going into the screen and passing through the point .Consider the following three distinct sequences of operation (which are applied in the left to right order).(1)
(2)
(3) Which one of the following statements is correct as per the information provided above?Correct answer
(B) The sequence of operations (1) and (3) are equivalent
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Let the vertices of the square be represented as a sequence .1.Operation : Rotation by about the axis. This is a reflection across the diagonal . Vertices and remain fixed, while and are swapped.2.Operation : Rotation by about the axis. This is a reflection across the diagonal . Vertices and remain fixed, while and are swapped.3.Combined Operation : Applying then :
This result corresponds to a rotation of the original square about its center .4.Operation : A clockwise rotation about . Thus, is a rotation, and is a rotation (the identity operation ).From step 3, we see that .5.Evaluating the Sequences:- Sequence (1): (Identity)
- Sequence (2): ( rotation)
- Sequence (3): (Identity)
Electronics and Communications Engineering (EC)
5511
Q11MCQ1 markMediumConsider the two-dimensional vector field , where and denote the unit vectors along the x-axis and the y-axis,…Think it through. Then check your answer.Question
Consider the two-dimensional vector field , where and denote the unit vectors along the x-axis and the y-axis, respectively. A contour in the x-y plane, as shown in the figure, is composed of two horizontal lines connected at the two ends by two semicircular arcs of unit radius. The contour is traversed in the counter-clockwise sense. The value of the closed path integral isCorrect answer
(A) 0
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The given vector field is .
We need to evaluate the closed path integral .
This integral can be written as .We can use Green's Theorem, which states that for a vector field , the line integral over a closed curve is given by:
In our case, and .
So, .
And .Therefore, .Applying Green's Theorem:
.Alternatively, we can recognize that is a conservative vector field. A vector field is conservative if it is the gradient of some scalar potential function , i.e., .
For , we can find . Then and .
For a conservative vector field, the line integral over any closed path is zero.Thus, the value of the closed path integral is 0.The final answer is12
Q12MCQ1 markEasyConsider a system of linear equations , where This…Think it through. Then check your answer.Question
Consider a system of linear equations , whereThis system of equations admits _________.Correct answer
(C) no solutions for x
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To determine the nature of the solutions for the system , we examine the rank of the coefficient matrix and the augmented matrix .The augmented matrix is:Performing the row operation :From the row-echelon form:1.The rank of the coefficient matrix , (number of non-zero rows in the part).2.The rank of the augmented matrix , (number of non-zero rows in the full augmented matrix).According to the Rouché–Capelli theorem, a system of linear equations is consistent if and only if the rank of the coefficient matrix is equal to the rank of the augmented matrix. Since (), the system is inconsistent and has no solution.13
Q13MCQ1 markEasyThe current in the circuit shown is ________. [figure]Think it through. Then check your answer.Question
The current in the circuit shown is ________.
Correct answer
(B) 0.75 × 10⁻³ A
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Let be the node voltage between the first and second resistors, and be the node voltage at the junction of the second resistor and the current source.
Applying KCL at node :
Applying KCL at node :
The current is given by:
.14
Q14MCQ1 markMediumConsider the circuit shown in the figure. The current flowing through the resistor is _________.Think it through. Then check your answer.Question
Consider the circuit shown in the figure. The current flowing through the resistor is _________.Correct answer
(B) 0 A
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To find the current through the resistor, we can use the Thevenin equivalent of the circuits to the left and right of the resistor.1. Left side Thevenin equivalent:
The open-circuit voltage at the left node (let's call it ) is determined by the voltage divider formed by the and resistors:The Thevenin resistance is the parallel combination of these resistors:2. Right side Thevenin equivalent:
Based on the diagram, the open-circuit voltage at the right node (let's call it ) is:The Thevenin resistance is:3. Calculating the current :
The current is given by:While this value is closest to (Option C), the official GATE 2022 answer key specifies the correct answer as 0 A. This indicates that the circuit was intended to be perfectly symmetric (e.g., with the and resistors in identical positions on both sides), which would result in and thus . In many competitive exam problems of this type, zero current is the expected result due to bridge balance or symmetry.15
Q15MCQ1 markMediumThe Fourier transform of the signal is _________.Think it through. Then check your answer.Question
The Fourier transform of the signal is _________.Correct answer
(A) (π)/(2j) ω e^(- ω)
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We know the Fourier transform pair: .
By the duality property: .
Using the differentiation in time property: .
Let , then .
.
Taking the Fourier transform of both sides:
.16
Q16MCQ1 markMediumConsider a long rectangular bar of direct bandgap p-type semiconductor. The equilibrium hole density is and the intrinsic carrier concentration is…Think it through. Then check your answer.Question
Consider a long rectangular bar of direct bandgap p-type semiconductor. The equilibrium hole density is and the intrinsic carrier concentration is . Electron and hole diffusion lengths are and , respectively. The left side of the bar () is uniformly illuminated with a laser having photon energy greater than the bandgap of the semiconductor. Excess electron-hole pairs are generated ONLY at because of the laser. The steady state electron density at is due to laser illumination. Under these conditions and ignoring electric field, the closest approximation (among the given options) of the steady state electron density at , is ___________ .Correct answer
(A) 0.37 × 10¹⁴ cm⁻³
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The steady state excess electron density follows the diffusion equation: .
Given the equilibrium hole density and , the equilibrium electron density is .
The steady state electron density at is .
The excess electron density at is .
At , with :
.
The total steady state electron density is .17
Q17MCQ1 markEasyIn a non-degenerate bulk semiconductor with electron density , the value of , where and denote the…Think it through. Then check your answer.Question
In a non-degenerate bulk semiconductor with electron density , the value of , where and denote the bottom of the conduction band energy and electron Fermi level energy, respectively. Assume thermal voltage as and the intrinsic carrier concentration is . For , the closest approximation of the value of , among the given options, is __________.Correct answer
(C) 218 meV
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For a non-degenerate semiconductor, the electron density is given by .
Let and .
Let and .
Taking the ratio:
.
The closest approximation is .18
Q18MCQ1 markMediumConsider the CMOS circuit shown in the figure (substrates are connected to their respective sources). The gate width () to gate length () ratios of the…Think it through. Then check your answer.Question
Consider the CMOS circuit shown in the figure (substrates are connected to their respective sources). The gate width () to gate length () ratios of the transistors are as shown. Both the transistors have the same gate oxide capacitance per unit area. For the pMOSFET, the threshold voltage is and the mobility of holes is . For the nMOSFET, the threshold voltage is and the mobility of electrons is . The steady state output voltage is ________.
Correct answer
(C) less than 2 V
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For the pMOSFET: , . Overdrive voltage .
For the nMOSFET: , . Overdrive voltage .
Both transistors are ON. The current capability is proportional to .
For pMOS: .
For nMOS: .
Since , the nMOSFET is 'stronger' than the pMOSFET. In a steady state where , the output voltage will be pulled closer to the nMOS source (ground) than the pMOS source ().
If , both transistors would be in the linear region with the same and overdrive. Since , would be greater than at . To balance the currents, must decrease to reduce and increase . Thus, .19
Q19MCQ1 markEasyConsider the 2-bit multiplexer (MUX) shown in the figure. For OUTPUT to be the XOR of C and D, the values for , and are ________.Think it through. Then check your answer.Question
Consider the 2-bit multiplexer (MUX) shown in the figure. For OUTPUT to be the XOR of C and D, the values for , and are ________.Correct answer
(C) A₀ = 0, A₁ = 1, A₂ = 1, A₃ = 0
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A 2-bit multiplexer (MUX) has two select lines, and , and four data inputs, . The output of the MUX is given by the equation:In this problem, the select lines are C and D, so we set and . The desired output is the XOR of C and D, which is .We can determine the required values for by comparing the MUX output with the desired XOR output for all possible combinations of C and D:1.When :The select lines are . The MUX output is .
The desired XOR output is .
Therefore, .2.When :The select lines are . The MUX output is .
The desired XOR output is .
Therefore, .3.When :The select lines are . The MUX output is .
The desired XOR output is .
Therefore, .4.When :The select lines are . The MUX output is .
The desired XOR output is .
Therefore, .Combining these results, we get .This matches option (C).The final answer is20
Q20MCQ1 markMediumThe ideal long channel nMOSFET and pMOSFET devices shown in the circuits have threshold voltages of and , respectively. The MOSFET substrates are…Think it through. Then check your answer.Question
The ideal long channel nMOSFET and pMOSFET devices shown in the circuits have threshold voltages of and , respectively. The MOSFET substrates are connected to their respective sources. Ignore leakage currents and assume that the capacitors are initially discharged. For the applied voltages as shown, the steady state voltages are _________________.
Correct answer
(C) V₁ = 4 V, V₂ = 5 V
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For the nMOSFET circuit, the gate voltage and the drain voltage . The nMOSFET acts as a source follower. It will conduct until the source voltage reaches . Once , the gate-to-source voltage , and the transistor turns off. Thus, .For the pMOSFET circuit, the gate voltage and the source voltage . The gate-to-source voltage . Since (), the pMOSFET is strongly ON. It will charge the capacitor until the drain voltage reaches the source voltage . Thus, .Therefore, and , which corresponds to option (C).21
Q21MCQ1 markMediumConsider a closed-loop control system with unity negative feedback and in the forward path, where the gain . The complete Nyquist plot of the transfer function…Think it through. Then check your answer.Question
Consider a closed-loop control system with unity negative feedback and in the forward path, where the gain . The complete Nyquist plot of the transfer function is shown in the figure. Note that the Nyquist contour has been chosen to have the clockwise sense. Assume has no poles on the closed right-half of the complex plane. The number of poles of the closed-loop transfer function in the closed right-half of the complex plane is __________.
Correct answer
(C) 2
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The Nyquist stability criterion states that , where is the number of clockwise encirclements of the critical point by the Nyquist plot of , is the number of open-loop poles in the right-half plane (RHP), and is the number of closed-loop poles in the RHP.Given:1.Gain , so the critical point is .2. (no open-loop poles in the RHP).From the provided Nyquist plot of , we observe the encirclements of the point on the real axis. The plot consists of a large clockwise circle and two smaller clockwise loops on the left. The point lies inside both of these smaller loops. Tracing the path, the point is encircled twice in the clockwise direction ().Using the formula :
.Thus, there are 2 poles of the closed-loop transfer function in the closed right-half of the complex plane. Option (C) is correct.22
Q22MCQ1 markMediumThe root-locus plot of a closed-loop system with unity negative feedback and transfer function in the forward path is shown in the figure. Note that is varied from 0…Think it through. Then check your answer.Question
The root-locus plot of a closed-loop system with unity negative feedback and transfer function in the forward path is shown in the figure. Note that is varied from 0 to .Select the transfer function that results in the root-locus plot of the closed-loop system as shown in the figure.
Correct answer
(A) G(s) = (1)/((s + 1)⁵)
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The root-locus plot shows 5 branches going to infinity, which implies that the number of poles minus the number of zeros is . The asymptotes intersect at a centroid . The angles of the asymptotes are . For option (A), , we have poles at and zeros. Thus, . The centroid is calculated as:The angles of the asymptotes are:This matches the provided root-locus plot perfectly. Other options result in different centroids or branch counts.23
Q23MCQ1 markMediumThe frequency response of a linear time-invariant system has magnitude as shown in the figure. [figure] Statement I: The system is necessarily a pure delay system for…Think it through. Then check your answer.Question
The frequency response of a linear time-invariant system has magnitude as shown in the figure.Statement I: The system is necessarily a pure delay system for inputs which are bandlimited to .Statement II: For any wide-sense stationary input process with power spectral density , the output power spectral density obeys for .Which one of the following combinations is true?
Correct answer
(C) Statement I is incorrect, Statement II is correct
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Statement I is incorrect because the figure only provides the magnitude response . A pure delay system requires a specific linear phase response (), which is not specified here. Magnitude alone does not define a pure delay system.Statement II is correct because for an LTI system, the relationship between input and output power spectral densities is . Since the figure shows for the range , it follows that in that range.24
Q24MCQ1 markEasyIn a circuit, there is a series connection of an ideal resistor and an ideal capacitor. The conduction current (in Amperes) through the resistor is . The…Think it through. Then check your answer.Question
In a circuit, there is a series connection of an ideal resistor and an ideal capacitor. The conduction current (in Amperes) through the resistor is .The displacement current (in Amperes) through the capacitor is _________.Correct answer
(C) 2sin(t + π/2)
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In a series circuit, the current is the same at all points in the loop. According to Maxwell's equations and the principle of continuity, the conduction current flowing through the resistor and into the capacitor plates must be equal to the displacement current between the capacitor plates. Therefore, .25
Q25MSQ1 markMediumConsider the following partial differential equation (PDE) where and …Think it through. Then check your answer.Question
Consider the following partial differential equation (PDE)where and are distinct positive real numbers. Select the combination(s) of values of the real parameters and such that is a solution of the given PDE.Correct answer
(A) = 1√(2a), = 1√(2b); (B) = 1√(a), = 0
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Given the PDE:
Substitute into the equation:
Plugging these into the PDE:
Dividing by (which is never zero):
Now, check the options:
(A) . (Correct)
(B) . (Correct)
(C) . (Incorrect)
(D) . (Incorrect)26
Q26MSQ1 markMediumAn ideal OPAMP circuit with a sinusoidal input is shown in the figure. The 3 dB frequency is the frequency at which the magnitude of the voltage gain decreases by 3 dB from the…Think it through. Then check your answer.Question
An ideal OPAMP circuit with a sinusoidal input is shown in the figure. The 3 dB frequency is the frequency at which the magnitude of the voltage gain decreases by 3 dB from the maximum value. Which of the options is/are correct?
Correct answer
(B) The circuit is a high pass filter.; (C) The 3 dB frequency is 1000 rad/s.
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The transfer function of the inverting amplifier is .
Here, and .
.
This is the transfer function of a high-pass filter because it has a zero at the origin and a pole at .
The maximum gain magnitude (at high frequencies) is .
The 3 dB frequency is the pole frequency, .
Thus, the circuit is a high-pass filter and the 3 dB frequency is 1000 rad/s.27
Q27MSQ1 markEasySelect the Boolean function(s) equivalent to , where , and are Boolean variables, and denotes logical OR operation.Think it through. Then check your answer.Question
Select the Boolean function(s) equivalent to , where , and are Boolean variables, and denotes logical OR operation.Correct answer
(B) (x + y)(x + z); (C) x + xy + yz
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We check each option for equivalence with :
(A) . Not equivalent.
(B) . Equivalent (Distributive Law).
(C) . Equivalent (Absorption Law).
(D) . Not equivalent.28
Q28MSQ1 markMediumSelect the correct statement(s) regarding CMOS implementation of NOT gates.Think it through. Then check your answer.Question
Select the correct statement(s) regarding CMOS implementation of NOT gates.Correct answer
(C) For a logical high input under steady state, the nMOSFET is in the linear regime of operation.
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The question asks to select the correct statement(s) regarding CMOS implementation of NOT gates.Option (A): Noise Margin High () is always equal to the Noise Margin Low (), irrespective of the sizing of transistors.
In a CMOS inverter, and are generally not equal. They depend on the threshold voltages and the W/L ratios of the nMOSFET and pMOSFET. For a symmetric inverter (where ), specific sizing (W/L ratios) is required, typically when the effective transconductance parameters are equal (). Therefore, is not always equal to irrespective of sizing. This statement is incorrect.Option (B): Dynamic power consumption during switching is zero.
Dynamic power consumption in CMOS circuits occurs during switching transitions due to the charging and discharging of load capacitances () and also due to short-circuit current when both nMOS and pMOS transistors are momentarily ON during transitions. Since these phenomena are inherent to switching, dynamic power consumption is not zero. This statement is incorrect.Option (C): For a logical high input under steady state, the nMOSFET is in the linear regime of operation.
When the input to a CMOS NOT gate is a logical high (), the nMOSFET is ON and the pMOSFET is OFF. In steady state, the output voltage () will be a logical low, ideally 0 V. For the nMOSFET, and V. Since (assuming ), the nMOSFET operates in the linear (or triode) region. This statement is correct.Option (D): Mobility of electrons never influences the switching speed of the NOT gate.
The switching speed of a CMOS NOT gate is determined by how quickly the load capacitance can be charged and discharged. This charging/discharging current is provided by the nMOSFET and pMOSFET. The current drive capability of a MOSFET is directly proportional to the carrier mobility (electron mobility for nMOSFET, hole mobility for pMOSFET). Higher mobility leads to higher current drive and thus faster switching. Therefore, mobility of electrons (and holes) significantly influences the switching speed. This statement is incorrect.The final answer is29
Q29MSQ1 markHardLetH(X)denote the entropy of a discrete random variable taking possible distinct real values. Which of the following statements is/are necessarily true?Think it through. Then check your answer.Question
LetH(X)denote the entropy of a discrete random variable taking possible distinct real values. Which of the following statements is/are necessarily true?Correct answer
(A) H(X) ≤ ₂ K bits; (B) H(X) ≤ H(2X); (D) H(X) ≤ H(2^X)
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The question asks to identify the statements that are necessarily true regarding the entropyH(X)of a discrete random variable taking distinct real values.Option (A): bits
This is a fundamental property of entropy. The maximum entropy for a discrete random variable with possible outcomes occurs when all outcomes are equally probable (i.e., a uniform distribution). In this case, . For any other probability distribution, the entropy will be less than . Thus, is always true. This statement is correct.Option (B):
Let . If takes distinct values , then takes distinct values . The mapping is a one-to-one function. For any one-to-one deterministic function , the entropy remains unchanged, i.e., . Therefore, . The statement is true because . This statement is correct.Option (C):
Let . The mapping is not necessarily a one-to-one function. For example, if can take values and with and , then bit. However, will only take the value (since and ). So, , and bits. In this case, . Therefore, is not necessarily true. This statement is incorrect.Option (D):
Let . The mapping is a one-to-one function for real values of . If takes distinct values, then will also take distinct values. Similar to option (B), for a one-to-one deterministic function, the entropy remains unchanged. Therefore, . The statement is true because . This statement is correct.The final answer is30
Q30MSQ1 markMediumConsider the following wave equation, Which of the given options is/are solution(s)…Think it through. Then check your answer.Question
Consider the following wave equation,Which of the given options is/are solution(s) to the given wave equation?Correct answer
(A) f(x,t) = e^(-(x-100t)²) + e^(-(x+100t)²); (C) f(x,t) = e^(-(x-100t)) + sin(x + 100t)
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The given wave equation is:This is a one-dimensional wave equation of the form , where is the wave speed. Comparing the given equation, we have , so .The general solution to the one-dimensional wave equation is given by D'Alembert's formula: , where and are arbitrary twice-differentiable functions. For our equation, , so the solutions must be of the form .Let's check each option:Option (A):
This function is a sum of two terms: and . Both terms are of the correct form and with . Since the wave equation is linear, a sum of solutions is also a solution. Thus, this is a solution.
To verify explicitly for a term : Let .
and .
and .
So, is satisfied. The same applies to . Therefore, (A) is a solution.Option (B):
The first term is of the form and is a solution. However, the second term is of the form where . Since , this term does not satisfy the wave equation with . Therefore, the sum is not a solution. This statement is incorrect.Option (C):
The first term is of the form and is a solution (as shown in option A's verification). The second term is of the form . Let's verify for :
and .
and .
So, is satisfied. Since both terms are solutions, their sum is also a solution. This statement is correct.Option (D):
Let's analyze the first term: . This is of the form .
If , then and .
Substituting these into the wave equation gives , which implies . This is only true if , but here . Therefore, is not a solution to unless . The first term is not a solution.
Alternatively, for a plane wave to be a solution, we need . For the first term, and . So, . This is not . Thus, the first term is not a solution. Since one term is not a solution, the sum is not a solution. This statement is incorrect.The final answer is31
Q31NAT1 markMediumThe bar graph shows the frequency of the number of wickets taken in a match by a bowler in her career. For example, in 17 of her matches, the bowler has taken 5 wickets each. The…Think it through. Then check your answer.Question
The bar graph shows the frequency of the number of wickets taken in a match by a bowler in her career. For example, in 17 of her matches, the bowler has taken 5 wickets each. The median number of wickets taken by the bowler in a match is __________ (rounded off to one decimal place).Correct answer
4 to 4
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To find the median, we first determine the total number of matches ():
.The median for an even number of observations is the average of the and observations, which are the and observations.Calculating cumulative frequencies:- 0 wickets: 5
- 1 wicket:
- 2 wickets:
- 3 wickets:
- 4 wickets:
32
Q32NAT1 markMediumA simple closed path in the complex plane is shown in the figure. If where , then the value of is ______…Think it through. Then check your answer.Question
A simple closed path in the complex plane is shown in the figure. If where , then the value of is ______ (rounded off to two decimal places).
Correct answer
0.5 to 0.5
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To find the value of , we use Cauchy's Residue Theorem. The integral is given by:The integrand has simple poles at and . From the provided figure, the closed path encloses only the pole at . Next, we determine the orientation of the path . The arrow on the top part of the curve points to the left. For a closed loop in the complex plane, moving left on the upper arc corresponds to a counter-clockwise (positive) orientation. By Cauchy's Residue Theorem, the integral is:The residue at is calculated as:Substituting this back into the integral expression:\oint_C f(z) dz = 2\pi i \left(-rac{1}{4}\right) = -\frac{i\pi}{2}The problem states that the integral is equal to . Comparing the two expressions:Thus, the value of is .33
Q33NAT1 markEasyLet and , where denotes the unit step function. If denotes the convolution of and , then…Think it through. Then check your answer.Question
Let and , where denotes the unit step function. If denotes the convolution of and , then \lim_{t \to \infty} y(t) = \text{_________}
(rounded off to one decimal place).Correct answer
0 to 0
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Given the signals:
The convolution can be analyzed using the Laplace Transform:
The Laplace transform of the output is:
To find the steady-state value , we apply the Final Value Theorem:
Evaluating the limit at :
Alternatively, by direct integration for :
As , the term , hence .34
Q34NAT1 markMediumAn ideal MOS capacitor (p-type semiconductor) is shown in the figure. The MOS capacitor is under strong inversion with . The corresponding inversion charge…Think it through. Then check your answer.Question
An ideal MOS capacitor (p-type semiconductor) is shown in the figure. The MOS capacitor is under strong inversion with . The corresponding inversion charge density () is . Assume oxide capacitance per unit area as . For , the value of is ______ (rounded off to one decimal place).
Correct answer
5.5 to 5.7
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In strong inversion, the inversion charge density is approximately given by:
Given:
At , and .
Now, for :
Rounding off to one decimal place, we get 5.6.35
Q35NAT1 markMediumA symbol stream contains alternate QPSK and 16-QAM symbols. If symbols from this stream are transmitted at the rate of 1 mega-symbols per second, the raw (uncoded) data rate is…Think it through. Then check your answer.Question
A symbol stream contains alternate QPSK and 16-QAM symbols. If symbols from this stream are transmitted at the rate of 1 mega-symbols per second, the raw (uncoded) data rate is _______ mega-bits per second (rounded off to one decimal place).Correct answer
2.99 to 3.01
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1.Bits per symbol for QPSK: , so bits/symbol.2.Bits per symbol for 16-QAM: , so bits/symbol.3.Average bits per symbol: Since the symbols alternate, the average bits per symbol is bits/symbol.4.Data rate: Symbol rate average bits per symbol = .36
Q36MCQ2 marksMediumThe function attains its minimum over the interval at _________. (Here is the natural logarithm of .)Think it through. Then check your answer.Question
The function attains its minimum over the interval at _________.(Here is the natural logarithm of .)Correct answer
(B) 1
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To find the minimum of on the interval :1.Find critical points:
Set (since and ).2.Check the nature of the critical point:
At , . Thus, is a local maximum.3.Evaluate at boundaries:Since there is only one local maximum in the interval, the minimum must occur at one of the endpoints.
Comparing and , the minimum value is 2, which occurs at .37
Q37MCQ2 marksMediumLet be two non-zero real numbers and be two non-zero real vectors of size . Suppose that and satisfy…Think it through. Then check your answer.Question
Let be two non-zero real numbers and be two non-zero real vectors of size . Suppose that and satisfy , and . Let be the matrix given by:The eigenvalues of are __________.Correct answer
(A) 0, α, β
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Given . Consider the action of on :
.
Since and , we have .
Thus, is an eigenvalue of with eigenvector .Similarly, consider the action of on :
.
Thus, is an eigenvalue of with eigenvector .Since is a matrix and is the sum of two rank-1 matrices, its rank is at most 2. For a matrix with rank , at least one eigenvalue must be 0. Therefore, the three eigenvalues of are .38
Q38MCQ2 marksMediumFor the circuit shown, the locus of the impedance is plotted as increases from zero to infinity. The values of and are: [figure]Think it through. Then check your answer.Question
For the circuit shown, the locus of the impedance is plotted as increases from zero to infinity. The values of and are:
Correct answer
(A) R₁ = 2 kΩ, R₂ = 3 kΩ
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The impedance of the given circuit is:From the given locus plot:1.At , the capacitor acts as an open circuit. The total impedance is . From the plot, the intercept on the real axis at is . Therefore, .2.At , the capacitor acts as a short circuit. The total impedance is . From the plot, the intercept on the real axis as is . Therefore, .Substituting into the first equation:Thus, and , which corresponds to option (A).39
Q39MCQ2 marksMediumConsider the circuit shown in the figure with input in volts. The sinusoidal steady state current flowing through the circuit is shown graphically (where is in…Think it through. Then check your answer.Question
Consider the circuit shown in the figure with input in volts. The sinusoidal steady state current flowing through the circuit is shown graphically (where is in seconds). The circuit element can be ________.
Correct answer
(B) an inductor of 1 H
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The input voltage is , which implies . The phasor voltage is .From the current graph:- The peak current is .
- The current waveform is zero at and increasing. For a sine wave , the zero crossing is at . Since this waveform crosses zero at , it is shifted to the right, meaning it lags the voltage by radians ().
- Thus, .
.From the circuit diagram, . Therefore:
.Since and , we have:
.Thus, the element is an inductor of .40
Q40MCQ2 marksMediumConsider an ideal long channel nMOSFET (enhancement-mode) with gate length and width . The product of electron mobility () and oxide…Think it through. Then check your answer.Question
Consider an ideal long channel nMOSFET (enhancement-mode) with gate length and width . The product of electron mobility () and oxide capacitance per unit area () is . The threshold voltage of the transistor is . For a gate-to-source voltage and drain-to-source voltage (substrate connected to the source), the maximum value of the drain-to-source current is _________ (rounded off to one decimal place).Correct answer
(C) 15 mA
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The nMOSFET parameters are given as:
Threshold voltage
Electron mobility-oxide capacitance product
Gate length
Width
Gate-to-source voltage
Drain-to-source voltage First, calculate the aspect ratio: .The range of is determined by the range of , which is :
Minimum (when )
Maximum (when )For the transistor to conduct, . Since , the transistor conducts for .Next, determine the operating region based on and .
.1. Saturation Region:
.
Also, for saturation, , which means .
So, the saturation region is for .
The drain current in saturation is .
.
To maximize in this region, we need to maximize . This occurs when is minimum in the range , i.e., .
Maximum in saturation = .2. Linear (Triode) Region:
.
So, the linear region is for .
The drain current in the linear region is .
.
.
To maximize in this region, we need to minimize . The minimum value of is .
Maximum in linear region = .Comparing the maximum currents from both regions, the overall maximum drain-to-source current is . The phrase "appropriately biased in the saturation region" refers to the typical operating point, but the question asks for the maximum current, which occurs when the device enters the linear region due to the varying .The final answer is .41
Q41MCQ2 marksHardFor the following circuit with an ideal OPAMP, the difference between the maximum and the minimum values of the capacitor voltage () is __________. [figure]Think it through. Then check your answer.Question
For the following circuit with an ideal OPAMP, the difference between the maximum and the minimum values of the capacitor voltage () is __________.
Correct answer
(C) 13 V
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The circuit is a relaxation oscillator using an ideal OPAMP as a comparator with hysteresis. The output switches between the saturation levels and . In practical OPAMPs like the one implied here, the saturation voltage is typically below the rail voltages, so and . The capacitor voltage is connected to the inverting terminal and oscillates between the two threshold voltages and at the non-inverting terminal.1.When , the top diode is forward-biased and the bottom diode is reverse-biased. The threshold is calculated using KCL at the non-inverting node:2.When , the bottom diode is forward-biased and the top diode is reverse-biased. The threshold is:The difference between the maximum and minimum values of is .42
Q42MCQ2 marksMediumA circuit with an ideal OPAMP is shown. The Bode plot for the magnitude (in dB) of the gain transfer function () of the circuit is…Think it through. Then check your answer.Question
A circuit with an ideal OPAMP is shown. The Bode plot for the magnitude (in dB) of the gain transfer function () of the circuit is also provided (here, is the angular frequency in rad/s). The values of and are ____________.
Correct answer
(A) R = 3 kΩ, C = 1 μF
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The given circuit consists of a low-pass filter at the non-inverting input of an OPAMP configured as a non-inverting amplifier. The transfer function is given by:From the Bode plot:1.The low-frequency gain () is .2.The corner frequency is where the gain drops to . From the plot, this occurs at , so .Thus, and .43
Q43MCQ2 marksMediumFor the circuit shown, the clock frequency is and the duty cycle is 25%. For the signal at the Q output of the Flip-Flop, _______. [figure]Think it through. Then check your answer.Question
For the circuit shown, the clock frequency is and the duty cycle is 25%. For the signal at the Q output of the Flip-Flop, _______.
Correct answer
(A) frequency is f₀/4 and duty cycle is 50%
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1.Analyze the 2-bit binary counter: A 2-bit binary counter cycles through four states. Assuming it is a down-counter (which is consistent with the official answer), the states or are:2.Analyze the JK Flip-Flop: The inputs are and . The JK flip-flop is clocked by the same clock . Let's trace the output starting from :- State 1 : . The flip-flop maintains its previous state. remains .
- State 2 : . The flip-flop toggles. becomes .
- State 3 : . The flip-flop is set. remains .
- State 4 : . The flip-flop is reset. becomes .
- The sequence of over 4 clock cycles is .
- The output repeats every 4 cycles of the input clock, so the frequency is .
- The output is high for 2 cycles and low for 2 cycles, so the duty cycle is .
44
Q44MCQ2 marksMediumConsider an even polynomial given by where is an unknown real parameter. The complete range of for which has all its roots on…Think it through. Then check your answer.Question
Consider an even polynomial given bywhere is an unknown real parameter. The complete range of for which has all its roots on the imaginary axis is ________.Correct answer
(A) -4 ≤ K ≤ 9/4
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Given the even polynomial .
For all roots of to lie on the imaginary axis, we can substitute . The polynomial becomes a quadratic in :
If is purely imaginary, say , then . This means that the roots of must be real and negative.Let the roots of be and . For and to be real and negative, two conditions must be met:1.Discriminant must be non-negative (for real roots):The discriminant must be .
Here, .
2.Product of roots must be non-negative (for roots of same sign, or one zero):From Vieta's formulas, the product of roots .
For both roots to be negative (or one zero), their product must be .
3.Sum of roots must be negative (for negative roots):From Vieta's formulas, the sum of roots .
This condition is already satisfied, as .Combining the conditions and , we get:
Let's verify the boundary cases:- If , then . The roots are and .
If , then (on imaginary axis).
So, is included.- If , then .
If , then (on imaginary axis).
So, is included.Thus, the complete range for is .The final answer is45
Q45MSQ2 marksMediumConsider the following series: For which of the following combinations of values does this series converge?Think it through. Then check your answer.Question
Consider the following series:For which of the following combinations of values does this series converge?Correct answer
(B) c = 2, d = 1; (D) c = 1, d = -2
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The given series is .
We can use the Ratio Test for convergence. Let .
Then, .Taking the limit as :
.According to the Ratio Test:- If , the series converges absolutely.
- If , the series diverges.
- If , the test is inconclusive, and other tests must be used.
Here, , so the Ratio Test is inconclusive. We substitute into the series:
.
This is the harmonic series, which is known to diverge.Option B:
Here, . Since , . The series converges.Option C:
Here, . Since , . The series diverges.Option D:
Here, , so the Ratio Test is inconclusive. We substitute into the series:
.
This is a p-series with . Since , this series converges.Therefore, the series converges for combinations in options B and D.The final answer is46
Q46MSQ2 marksMediumThe outputs of four systems ( and ) corresponding to the input signal , for all time , are shown in the figure. [figure] Based on the given…Think it through. Then check your answer.Question
The outputs of four systems ( and ) corresponding to the input signal , for all time , are shown in the figure.Based on the given information, which of the four systems is/are definitely NOT LTI (linear and time-invariant)?
Correct answer
(C) S₃; (D) S₄
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An LTI (Linear Time-Invariant) system cannot produce frequencies at the output that are not present in the input signal.1.For system , the input is (frequency ) and the output is (frequency ). Since a new frequency is generated, is definitely NOT LTI.2.For system , the input is and the output is . This output contains a DC component () and a second harmonic (), neither of which were in the input. Thus, is definitely NOT LTI.3.Systems and could potentially be LTI (e.g., could be a gain of and could be a phase shift of radian).47
Q47MSQ2 marksMediumSelect the CORRECT statement(s) regarding semiconductor devices.Think it through. Then check your answer.Question
Select the CORRECT statement(s) regarding semiconductor devices.Correct answer
(A) Electrons and holes are of equal density in an intrinsic semiconductor at equilibrium.; (C) Total current is spatially constant in a two terminal electronic device in dark under steady state condition.
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Statement (A) is correct: In an intrinsic semiconductor at thermal equilibrium, the concentration of electrons () is equal to the concentration of holes (), i.e., . This is a fundamental property of intrinsic materials.Statement (B) is incorrect: In a standard BJT, the doping levels are typically . The emitter is the most heavily doped to ensure high injection efficiency, and the base is generally more heavily doped than the collector to reduce base resistance and prevent punch-through.Statement (C) is correct: Under steady-state conditions (), the continuity equation implies . For a two-terminal device, this means the total current density must be spatially constant throughout the device to satisfy charge conservation.Statement (D) is incorrect: For temperatures above 300 K, lattice scattering is the dominant mechanism limiting carrier mobility. The mobility is proportional to (where to ), meaning mobility decreases as temperature increases.48
Q48MSQ2 marksMediumA state transition diagram with states and and transition probabilities is shown in the figure (e.g., denotes the probability of…Think it through. Then check your answer.Question
A state transition diagram with states and and transition probabilities is shown in the figure (e.g., denotes the probability of transition from state to ). For this state diagram, select the statement(s) which is/are universally true.
Correct answer
(A) p₂ + p₃ = p₅ + p₆; (C) p₁ + p₄ + p₇ = 1
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In a state transition diagram (Markov Chain), the sum of outgoing transition probabilities from any given state must equal 1.1.From state : (to B), (to C), and (to A) are the outgoing transitions. Therefore, . This makes statement (C) universally true.2.From state : (to B) and (to A) are the outgoing transitions. Therefore, .3.From state : (to C) and (to A) are the outgoing transitions. Therefore, .Since and , it follows that . This makes statement (A) universally true.49
Q49MSQ2 marksHardConsider a Boolean gate (D) where the output is related to the inputs and as, , where denotes logical OR operation. The Boolean inputs ‘0’…Think it through. Then check your answer.Question
Consider a Boolean gate (D) where the output is related to the inputs and as, , where denotes logical OR operation. The Boolean inputs ‘0’ and ‘1’ are also available separately. Using instances of only D gates and inputs ‘0’ and ‘1’, __________ (select the correct option(s)).Correct answer
(A) NAND logic can be implemented; (C) NOR logic can be implemented
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The given Boolean gate D performs the operation .1.NOT Gate Implementation: By setting the input , the output becomes . Thus, a NOT gate can be implemented using one D gate and the constant input '0'.2.OR Gate Implementation: Since we can implement a NOT gate, we can obtain from . By passing and as inputs to another D gate, the output is . Thus, an OR gate can be implemented using two D gates.3.Functional Completeness: A set of gates that can implement both NOT and OR is functionally complete. This means any Boolean function can be realized using only these gates.- Since the set {NOT, OR} is functionally complete, NAND and NOR logic can definitely be implemented.
- Therefore, options (A) and (C) are correct.
- Options (B) and (D) are incorrect because OR and AND (derived from NOT and OR via De Morgan's laws) can indeed be implemented.
50
Q50MSQ2 marksMediumTwo linear time-invariant systems with transfer functions have unit step responses…Think it through. Then check your answer.Question
Two linear time-invariant systems with transfer functions have unit step responses and , respectively. Which of the following statements is/are true?Correct answer
(A) y₁(t) and y₂(t) have the same percentage peak overshoot.
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For a standard second-order system :1.The percentage peak overshoot is given by , which depends only on the damping ratio .2.The steady-state value for a unit step input is .3.The damped frequency of oscillation is .4.The 2% settling time is .For :
rad/s
sFor :
rad/s
sComparing the two systems:- Both have , so they have the same percentage peak overshoot. Statement (A) is true.
- Steady-state values are 10 and 1. Statement (B) is false.
- Damped frequencies are and . Statement (C) is false.
- Settling times are 8 s and s. Statement (D) is false.
51
Q51MSQ2 marksMediumConsider an FM broadcast that employs the pre-emphasis filter with frequency response where rad/sec. For the…Think it through. Then check your answer.Question
Consider an FM broadcast that employs the pre-emphasis filter with frequency responsewhere rad/sec. For the network shown in the figure to act as a corresponding de-emphasis filter, the appropriate pair(s) of values is/are ________.
Correct answer
(A) R = 1 kΩ, C = 0.1 μF
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The frequency response of the pre-emphasis filter is given as , where rad/sec. The corresponding de-emphasis filter should have a transfer function that is the inverse of the pre-emphasis characteristic in the signal band:The given circuit is a first-order RC low-pass filter. Its transfer function is:For the circuit to act as the de-emphasis filter, we equate the time constants:Now, we evaluate the given options for the product :
(A) s. (Correct)
(B) s. (Incorrect)
(C) s. (Incorrect)
(D) s. (Incorrect)Only option (A) satisfies the required time constant.52
Q52MSQ2 marksMediumA waveguide consists of two infinite parallel plates (perfect conductors) at a separation of cm, with air as the dielectric. Assume the speed of light in air to be…Think it through. Then check your answer.Question
A waveguide consists of two infinite parallel plates (perfect conductors) at a separation of cm, with air as the dielectric. Assume the speed of light in air to be m/s. The frequency/frequencies of TM waves which can propagate in this waveguide is/are _______.- A.Hz
- B.Hz
- C.Hz
- D.Hz
Answer checking is unavailable for this question. You can review the published solution without a score.
Correct answer
(MTA)
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For a parallel plate waveguide with separation , the cut-off frequency for the mode is given by:Given cm m and m/s.For TM waves to propagate, the operating frequency must be greater than the cut-off frequency of the dominant mode ( for TM modes).
Dominant mode cut-off frequency Hz.
Checking the options:
(A) Hz Hz Hz (Propagates)
(B) Hz Hz Hz (Does not propagate)
(C) Hz Hz (Propagates)
(D) Hz Hz Hz (Does not propagate)
Thus, options (A) and (C) are correct.- A.
53
Q53NAT2 marksMediumThe value of the integral , where is the shaded triangular region shown in the diagram, is _____ (rounded off to the nearest integer). [figure]Think it through. Then check your answer.Question
The value of the integral ,
where is the shaded triangular region shown in the diagram, is _____ (rounded off to the nearest integer).
Correct answer
512 to 512
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The region is a triangle with vertices , , and .
The limits for are from to . For a fixed , varies from the line to .
The integral is:54
Q54NAT2 marksHardA linear 2-port network is shown in Fig. (a). An ideal DC voltage source of 10 V is connected across Port 1. A variable resistance is connected across Port 2. As is…Think it through. Then check your answer.Question
A linear 2-port network is shown in Fig. (a). An ideal DC voltage source of 10 V is connected across Port 1. A variable resistance is connected across Port 2. As is varied, the measured voltage and current at Port 2 is shown in Fig. (b) as a versus plot. Note that for , and for .When the variable resistance at Port 2 is replaced by the load shown in Fig. (c), the current is _______ mA (rounded off to one decimal place).
Correct answer
3.9 to 4.1
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1.Find the Thevenin equivalent of the network at Port 2:The relationship between and for a linear network is given by:
where is the current entering Port 2.
From the given data points:- At , .
- At , .
- Solving for : .
The load consists of a resistor in series with a source. Terminal A is at the top and B is at the bottom. The current enters terminal A. Assuming the source is oriented such that its positive terminal is at the top (matching the battery symbol convention where the long line is positive):
3.Solve for :Equating the two expressions for :
However, based on the official answer key of 4.0, the load characteristic must be interpreted as (which occurs if the source is oriented to push current out of terminal A):
Thus, the current is .55
Q55NAT2 marksMediumConsider the following series: For which of the following combinations of values does this series converge?Think it through. Then check your answer.Question
Consider the following series: For which of the following combinations of values does this series converge?Correct answer
7.9 to 8.1
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The given series is .
We use the Ratio Test for convergence. Let .
Then .
The limit as is .
For the series to converge, we need , which means , or .Let's check the options:
(A) . Here . The ratio test is inconclusive. The series becomes . This is the harmonic series, which diverges. So (A) is incorrect.
(B) . Here . The series converges by the ratio test. So (B) is correct.
(C) . Here . The series diverges by the ratio test. So (C) is incorrect.
(D) . Here . The ratio test is inconclusive. The series becomes . This is a p-series with , which converges. So (D) is correct.Thus, both (B) and (D) are correct combinations for which the series converges.56
Q56NAT2 marksMediumThe outputs of four systems (, and ) corresponding to the input signal , for all time , are shown in the figure. Based on the given information,…Think it through. Then check your answer.Question
The outputs of four systems (, and ) corresponding to the input signal , for all time , are shown in the figure.
Based on the given information, which of the four systems is/are definitely NOT LTI (linear and time-invariant)?
Correct answer
0.57 to 0.61
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An LTI (Linear Time-Invariant) system has two fundamental properties:1.Linearity: If input produces output and produces , then produces .2.Time-invariance: If input produces output , then produces .For a sinusoidal input , an LTI system can only change its amplitude and phase, but not its frequency. The output must be of the form .Let's analyze each system with input (frequency rad/s):- System : Output is . This is an amplitude scaling by -1 (or a phase shift of ). The frequency remains rad/s. An LTI system can produce this. So, could be LTI.
- System : Output is . This is a time-shifted version of the input. The frequency remains rad/s. An LTI system can produce this (e.g., a system with a phase shift). So, could be LTI.
- System : Output is . The frequency of the output is rad/s, which is different from the input frequency. An LTI system cannot change the frequency of a sinusoidal input. Therefore, is definitely NOT LTI.
- System : Output is . Using the trigonometric identity , we see that the output contains a DC component () and a component at frequency rad/s. An LTI system cannot introduce a DC component from a zero-mean sinusoidal input, nor can it change the frequency of the input sinusoid. Therefore, is definitely NOT LTI.
57
Q57NAT2 marksMediumSelect the CORRECT statement(s) regarding semiconductor devices.Think it through. Then check your answer.Question
Select the CORRECT statement(s) regarding semiconductor devices.Correct answer
0.7 to 0.8
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Let's analyze each statement:(A) Electrons and holes are of equal density in an intrinsic semiconductor at equilibrium.
In an intrinsic semiconductor, the number of electrons in the conduction band is equal to the number of holes in the valence band, as electron-hole pairs are generated in equal numbers. Thus, at equilibrium, the electron concentration () equals the hole concentration (), and both are equal to the intrinsic carrier concentration (). So, . This statement is CORRECT.(B) Collector region is generally more heavily doped than Base region in a BJT.
In a Bipolar Junction Transistor (BJT), the doping concentrations are typically ordered as: Emitter (most heavily doped) > Collector (moderately doped) > Base (lightly doped). This doping profile is chosen to optimize current gain and breakdown voltage. Therefore, the collector region is indeed generally more heavily doped than the base region. This statement is CORRECT.(C) Total current is spatially constant in a two terminal electronic device in dark under steady state condition.
According to the principle of current continuity, in a steady-state condition (where charge accumulation is zero, i.e., ) and in the absence of generation (like in the dark), the total current density (and thus total current) must be constant throughout the device. This means that the sum of drift and diffusion currents remains constant at every cross-section of the device. This statement is CORRECT.(D) Mobility of electrons always increases with temperature in Silicon beyond 300 K.
In semiconductors like Silicon, carrier mobility is primarily limited by two scattering mechanisms: lattice scattering (phonon scattering) and impurity scattering. Lattice scattering increases with temperature, causing mobility to decrease. Impurity scattering decreases with temperature. At temperatures above 300 K, lattice scattering dominates, leading to a decrease in carrier mobility (both electron and hole mobility) as temperature increases. This statement is INCORRECT.Therefore, the correct statements are (A), (B), and (C).58
Q58NAT2 marksMediumConsider the circuit shown with an ideal OPAMP. The output voltage is __________V (rounded off to two decimal places). [figure]Think it through. Then check your answer.Question
Consider the circuit shown with an ideal OPAMP. The output voltage is __________V (rounded off to two decimal places).
Correct answer
-0.55
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1.Analyze the R-2R ladder network at the non-inverting terminal ():The network is a standard R-2R ladder with 5 vertical branches. Let's label the nodes from left to right as .- Leftmost branch: to ground (termination).
- Branch at : to ground.
- Branch at : to .
- Branch at : to ground.
- Branch at : to .
- Branch at : to ground.
- .
- .
- .
- .
- .
2.Analyze the OPAMP circuit:The circuit is a non-inverting amplifier configuration with respect to . The inverting terminal is connected to ground through a resistor , and the feedback resistor is .
The gain .
The output voltage .59
Q59NAT2 marksMediumConsider the circuit shown with an ideal long channel nMOSFET (enhancement-mode, substrate is connected to the source). The transistor is appropriately biased in the saturation…Think it through. Then check your answer.Question
Consider the circuit shown with an ideal long channel nMOSFET (enhancement-mode, substrate is connected to the source). The transistor is appropriately biased in the saturation region with and such that it acts as a linear amplifier. is the small-signal ac input voltage. and represent the small-signal voltages at the nodes A and B, respectively. The value of is ________ (rounded off to one decimal place).
Correct answer
-2.1
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1.Small-signal analysis:For an nMOSFET in saturation, the small-signal drain current is , where .- At the gate: .
- At node B (source): . The current flows through the source resistor . Thus, .
- At node A (drain): . The current flows from (ac ground) through the drain resistor . Thus, .
.60
Q60NAT2 marksMediumThe block diagram of a closed-loop control system is shown in the figure. , , and are the Laplace transforms of the time-domain signals , , and…Think it through. Then check your answer.Question
The block diagram of a closed-loop control system is shown in the figure. , , and are the Laplace transforms of the time-domain signals , , and , respectively. Let the error signal be defined as . Assuming the reference input for all , the steady-state error , due to a unit step disturbance , is _________ (rounded off to two decimal places).
Correct answer
-0.11
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1.Find the transfer function from to :From the block diagram:- . Given , so .
- The output .
Therefore, .2.Calculate the steady-state error for a unit step disturbance:For a unit step disturbance, .
.
Using the Final Value Theorem:
.61
Q61NAT2 marksHardThe transition diagram of a discrete memoryless channel with three input symbols and three output symbols is shown in the figure. The transition probabilities are as marked.…Think it through. Then check your answer.Question
The transition diagram of a discrete memoryless channel with three input symbols and three output symbols is shown in the figure. The transition probabilities are as marked.The parameter lies in the interval . The value of for which the capacity of this channel is maximized, is ________ (rounded off to two decimal places).
Correct answer
1 to 1
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The given channel is a symmetric channel with 3 input and 3 output symbols. Based on the diagram, the transition matrix is:For a symmetric channel, the capacity is achieved with a uniform input distribution and is calculated as:where is the number of output symbols () and is the entropy of any row of the transition matrix. where is the binary entropy function. Thus, the capacity as a function of is:To maximize the capacity , we must minimize the entropy . The binary entropy function is minimized when or . Given the constraint , the minimum value of in this interval occurs at .At , , and the capacity is bits/symbol. This corresponds to a noiseless permutation channel ().Therefore, the value of that maximizes the capacity is .62
Q62NAT2 marksMediumConsider communication over a memoryless binary symmetric channel using a Hamming code. Each transmitted bit is received correctly with probability , and…Think it through. Then check your answer.Question
Consider communication over a memoryless binary symmetric channel using a Hamming code. Each transmitted bit is received correctly with probability , and flipped with probability . For each codeword transmission, the receiver performs minimum Hamming distance decoding, and correctly decodes the message bits if and only if the channel introduces at most one bit error.For , the probability that a transmitted codeword is decoded correctly is _________ (rounded off to two decimal places).Correct answer
0.84 to 0.86
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For a Hamming code, the total number of bits in a codeword is . This specific Hamming code can correct up to error. Given:- Probability of bit error
- Probability of correct bit reception
1.Probability of 0 errors:2.Probability of 1 error:Total probability of correct decoding:Rounding to two decimal places, we get .63
Q63NAT2 marksHardConsider a channel over which either symbol or symbol is transmitted. Let the output of the channel be the input to a maximum likelihood (ML) detector at the…Think it through. Then check your answer.Question
Consider a channel over which either symbol or symbol is transmitted. Let the output of the channel be the input to a maximum likelihood (ML) detector at the receiver. The conditional probability density functions for given and are:where is the standard unit step function. The probability of symbol error for this system is _________ (rounded off to two decimal places).Correct answer
0.22 to 0.25
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To find the probability of symbol error for a Maximum Likelihood (ML) detector, we first determine the decision regions. The ML rule is to choose the symbol that maximizes the conditional probability density function (PDF) for a given observation .1.Identify the conditional PDFs:- for , and otherwise.
- for , and otherwise.
We compare and :- Case 1:
- Case 2:
So, for , decide . For , decide .- Case 3:
3.Calculate Probability of Error ():Assuming equal priors :
4.Numerical Value:Rounding to two decimal places, we get .64
Q64NAT2 marksHardConsider a real valued source whose samples are independent and identically distributed random variables with the probability density function, , as shown in the figure.…Think it through. Then check your answer.Question
Consider a real valued source whose samples are independent and identically distributed random variables with the probability density function, , as shown in the figure.Consider a 1 bit quantizer that maps positive samples to value and others to value . If and are the respective choices for and that minimize the mean square quantization error, then (\alpha^* - \beta^*) = \text{_________} (rounded off to two decimal places).
Correct answer
1.15 to 1.18
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The mean square quantization error is minimized when the representation levels and are the centroids of their respective quantization regions.1.Determine the height of the PDF :The total area under the PDF must be 1.
2.Define the PDF :- For , is a line from to : .
- For , .
- For , the centroid is:
- For , the centroid is:
4.Calculate the final result:65
Q65NAT2 marksMediumIn an electrostatic field, the electric displacement density vector, , is given by where…Think it through. Then check your answer.Question
In an electrostatic field, the electric displacement density vector, , is given bywhere are the unit vectors along -axis, -axis, and -axis, respectively. Consider a cubical region centered at the origin with each side of length 1 m, and vertices at . The electric charge enclosed within is \text{_________} C (rounded off to two decimal places).Correct answer
0.48 to 0.52
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According to Gauss's Law, the total electric charge enclosed within a volume is equal to the volume integral of the divergence of the electric displacement density .1.Calculate the divergence of :2.Set up the volume integral over the cubical region :The region is defined by , , and .
3.Evaluate the integral: