The PYQ practice room
GATE EE 2015 Set 1
All 65 solved GATE EE 2015 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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65
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100
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General Aptitude (GA)
101
Q1MCQ1 markEasyDidn't you buy ________ when you went shopping?Think it through. Then check your answer.Question
Didn't you buy ________ when you went shopping?Correct answer
(A) any paper
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In negative interrogative sentences, 'any' is used with uncountable nouns like 'paper' to ask about the presence of something. 'Didn't you buy any paper...' is the correct grammatical structure.2
Q2MCQ1 markEasyWhich of the following options is the closest in meaning to the sentence below? She enjoyed herself immensely at the party.Think it through. Then check your answer.Question
Which of the following options is the closest in meaning to the sentence below?She enjoyed herself immensely at the party.Correct answer
(C) She had a terrific time at the party
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'Terrific' is a synonym for 'extremely good' or 'immense enjoyment', which matches the meaning of 'enjoyed herself immensely'. 'Terrible', 'horrible', and 'terrifying' have negative meanings.3
Q3MCQ1 markMediumWhich one of the following combinations is incorrect?Think it through. Then check your answer.Question
Which one of the following combinations is incorrect?Correct answer
(B) Wheedle - Roundabout
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The pairs in A, C, and D are synonyms. 'Wheedle' means to coax or persuade through flattery, whereas 'roundabout' means indirect. Thus, the combination in B is incorrect.4
Q4MCQ1 markEasyBased on the given statements, select the most appropriate option to solve the given question. If two floors in a certain building are 9 feet apart, how many steps are there in a…Think it through. Then check your answer.Question
Based on the given statements, select the most appropriate option to solve the given question.
If two floors in a certain building are 9 feet apart, how many steps are there in a set of stairs that extends from the first floor to the second floor of the building?
Statements:
(I) Each step is 3/4 foot high.
(II) Each step is 1 foot wide.Correct answer
(A) Statement I alone is sufficient, but statement II alone is not sufficient.
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To find the number of steps, we need to know the total vertical distance between the floors and the height of each step.Given:
Total vertical distance between two floors = 9 feet.Statement (I): Each step is 3/4 foot high.
From this statement, we can calculate the number of steps: Number of steps = steps.
So, Statement I alone is sufficient.Statement (II): Each step is 1 foot wide.
This statement gives information about the width of the step, which is irrelevant to the number of steps required to cover a vertical distance. So, Statement II alone is not sufficient.Therefore, Statement I alone is sufficient, but Statement II alone is not sufficient.The correct option is (A).5
Q5MCQ1 markEasyGiven Set A = and Set B = , two numbers are randomly selected, one from each set. What is the probability that the sum of the two numbers…Think it through. Then check your answer.Question
Given Set A = and Set B = , two numbers are randomly selected, one from each set. What is the probability that the sum of the two numbers equals 16?Correct answer
(A) 0.20
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Let be the number of elements in Set A, and be the number of elements in Set B.
Set A = , so .
Set B = , so .When two numbers are randomly selected, one from each set, the total number of possible pairs is .We need to find pairs where , , such that .
Let's list the possible pairs:
If , then . is a valid pair since .
If , then . is a valid pair since .
If , then . is a valid pair since .
If , then . is a valid pair since .The favorable outcomes are 4 pairs: .Number of favorable outcomes = 4.
Total number of possible outcomes = 20.Probability = .The correct option is (A).6
Q6MCQ2 marksEasySelect the alternative meaning of the underlined part of the sentence. The chain snatchers took to their heels when the police party arrived.Think it through. Then check your answer.Question
Select the alternative meaning of the underlined part of the sentence.
The chain snatchers took to their heels when the police party arrived.Correct answer
(C) took to flight
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The idiom "took to their heels" means to run away or flee, typically in a hurry or to escape from something.Let's analyze the given options:
(A) "took shelter in a thick jungle" implies hiding, not necessarily running away.
(B) "open indiscriminate fire" means to start shooting randomly, which is not related to the idiom.
(C) "took to flight" means to flee or run away, which perfectly matches the meaning of "took to their heels".
(D) "unconditionally surrendered" means to give up without any demands, which is the opposite of running away.Therefore, the closest meaning to "took to their heels" is "took to flight".The correct option is (C).7
Q7MCQ2 marksEasyThe given statement is followed by some courses of action. Assuming the statement to be true, decide the correct option. Statement: There has been a significant drop in the…Think it through. Then check your answer.Question
The given statement is followed by some courses of action. Assuming the statement to be true, decide the correct option.Statement:There has been a significant drop in the water level in the lakes supplying water to the city.Course of action:(I) The water supply authority should impose a partial cut in supply to tackle the situation.
(II) The government should appeal to all the residents through mass media for minimal use of water.
(III) The government should ban the water supply in lower areas.Correct answer
(A) Statements I and II follow.
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Course of action (I) is a logical and immediate step to conserve the remaining water supply. Course of action (II) is a proactive measure to reduce overall demand through public cooperation. Course of action (III) is discriminatory and not a standard or fair administrative response to a general water shortage. Therefore, only statements I and II follow.8
Q8NAT2 marksMediumThe pie chart below has the breakup of the number of students from different departments in an engineering college for the year 2012. The proportion of male to female students in…9
Q9MCQ2 marksMediumThe probabilities that a student passes in Mathematics, Physics and Chemistry are , , and respectively. Of these subjects, the student has 75% chance of passing in at…Think it through. Then check your answer.Question
The probabilities that a student passes in Mathematics, Physics and Chemistry are , , and respectively. Of these subjects, the student has 75% chance of passing in at least one, a 50% chance of passing in at least two and a 40% chance of passing in exactly two. Following relations are drawn in , , :(I)
(II)
(III)Correct answer
(D) Relations I and III are true.
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Let .
.
.
.
Subtracting the two equations:
. This confirms relation (III).
Now, .
From , we have .
Substitute into the union formula:
. This confirms relation (I).
Thus, relations I and III are true.10
Q10MCQ2 marksEasyThe number of students in a class who have answered correctly, wrongly, or not attempted each question in an exam, are listed in the table below. The marks for each question are…Think it through. Then check your answer.Question
The number of students in a class who have answered correctly, wrongly, or not attempted each question in an exam, are listed in the table below. The marks for each question are also listed. There is no negative or partial marking.What is the average of the marks obtained by the class in the examination?Q No. Marks Answered Correctly Answered Wrongly Not Attempted 1 2 21 17 6 2 3 15 27 2 3 1 11 29 4 4 2 23 18 3 5 5 31 12 1 Correct answer
(C) 6.795
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1.First, determine the total number of students in the class. Summing the columns for any question (Correct + Wrong + Not Attempted) gives: students.2.Calculate the total marks obtained by the entire class by summing the marks for each question multiplied by the number of correct answers:- Q1:
- Q2:
- Q3:
- Q4:
- Q5:
3.Calculate the average marks: .Rounding to three decimal places, we get 6.795.
Electrical Engineering
5511
Q11NAT1 markMediumA random variable has probability density function as given below: If the…Think it through. Then check your answer.Question
A random variable has probability density function as given below:If the expected value , then is ___________.Correct answer
0.25 to 0.25
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1.Use the normalization property of PDF: .(Equation 1).2.Use the expected value formula: .(Equation 2).3.Solve the system of equations:From (1), . Substitute into (2):
.
Then .
So, for .4.Calculate :.12
Q12MCQ1 markEasyIf a continuous function does not have a root in the interval , then which one of the following statements is TRUE?Think it through. Then check your answer.Question
If a continuous function does not have a root in the interval , then which one of the following statements is TRUE?Correct answer
(C) f(a) · f(b) 0
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According to the Intermediate Value Theorem, if a continuous function takes values of opposite signs at the endpoints of an interval (i.e., ), then there must be at least one root in the interval . Conversely, if the function is continuous and has no root in the closed interval , it must maintain the same sign throughout the interval. Therefore, and must have the same sign, which implies .13
Q13NAT1 markMediumIf the sum of the diagonal elements of a matrix is , then the maximum possible value of determinant of the matrix is ________.Think it through. Then check your answer.Question
If the sum of the diagonal elements of a matrix is , then the maximum possible value of determinant of the matrix is ________.Correct answer
9 to 9
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Let the eigenvalues of the matrix be and . The sum of the diagonal elements of a matrix is equal to the sum of its eigenvalues (Trace).The determinant of the matrix is equal to the product of its eigenvalues.To find the maximum value of the product given their sum is constant, we use the property that the product of two numbers with a constant sum is maximized when the numbers are equal (assuming real eigenvalues).Thus, the maximum possible value of the determinant is:14
Q14MCQ1 markHardConsider a function , where is the distance from the origin and is the unit vector in the radial direction. The divergence of this…Think it through. Then check your answer.Question
Consider a function , where is the distance from the origin and is the unit vector in the radial direction. The divergence of this function over a sphere of radius , which includes the origin, isCorrect answer
(C) 4π
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The function is given as . According to the properties of the Dirac delta function in three dimensions:The question asks for the divergence 'over a sphere', which implies the volume integral of the divergence over the sphere of radius that includes the origin.Alternatively, using the Gauss Divergence Theorem:For a sphere of radius , the surface element is .15
Q15MCQ1 markEasyWhen the Wheatstone bridge shown in the figure is used to find the value of resistor , the galvanometer indicates zero current when , …Think it through. Then check your answer.Question
When the Wheatstone bridge shown in the figure is used to find the value of resistor , the galvanometer indicates zero current when , and . If is known with tolerance on its nominal value of , what is the range of in Ohms?
Correct answer
(A) [123.50, 136.50]
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For a balanced Wheatstone bridge, the condition is:Given and . The nominal value of is with a tolerance of .Calculating the range for :Thus, the range of is .16
Q16NAT1 markEasyA (0-50 A) moving coil ammeter has a voltage drop of 0.1 V across its terminals at full scale deflection. The external shunt resistance (in milliohms) needed to extend its range…Think it through. Then check your answer.Question
A (0-50 A) moving coil ammeter has a voltage drop of 0.1 V across its terminals at full scale deflection. The external shunt resistance (in milliohms) needed to extend its range to (0 – 500 A) is _________.Correct answer
0.22 to 0.23
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Given:
Full scale meter current, A
Voltage drop at full scale, V
Meter resistance,
Desired full scale current, A
Multiplying factor,
Shunt resistance required,
Thus, the shunt resistance needed is approximately milliohms.17
Q17MCQ1 markEasyOf the four characteristics given below, which are the major requirements for an instrumentation amplifier? P. High common mode rejection ratio Q. High input impedance R. High…Think it through. Then check your answer.Question
Of the four characteristics given below, which are the major requirements for an instrumentation amplifier?P. High common mode rejection ratio
Q. High input impedance
R. High linearity
S. High output impedanceCorrect answer
(A) P, Q and R only
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An instrumentation amplifier is designed to amplify very small differential signals while rejecting large common-mode signals. Its key requirements are:1.High Common Mode Rejection Ratio (CMRR) (P): To reject noise common to both inputs.2.High Input Impedance (Q): To prevent loading of the signal source.3.High Linearity (R): To ensure the output is a faithful reproduction of the input.4.Low Output Impedance: To drive subsequent stages without signal loss. (Characteristic S, high output impedance, is incorrect).Therefore, P, Q, and R are the major requirements.18
Q18NAT1 markMediumIn the following chopper, the duty ratio of switch S is 0.4. If the inductor and capacitor are sufficiently large to ensure continuous inductor current and ripple free capacitor…Think it through. Then check your answer.Question
In the following chopper, the duty ratio of switch S is 0.4. If the inductor and capacitor are sufficiently large to ensure continuous inductor current and ripple free capacitor voltage, the charging current (in Ampere) of the 5 V battery, under steady-state, is_______.
Correct answer
1 to 1
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The given circuit is a step-down (buck) chopper.
Input voltage, V
Duty ratio,
Average output voltage, V
The load consists of a resistor and a battery V in series.
Under steady-state, the average current flowing into the battery is:
A19
Q19NAT1 markMediumA moving average function is given by . If the input is a sinusoidal signal of frequency Hz, then in steady…Think it through. Then check your answer.Question
A moving average function is given by . If the input is a sinusoidal signal of frequency Hz, then in steady state, the output will lag (in degree) by ______.Correct answer
90 to 90
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The transfer function of the moving average filter is given by:For a sinusoidal input with frequency Hz, the angular frequency is:Substituting into the transfer function:Since :The phase angle of the transfer function is , which means the output lags the input by .20
Q20MCQ1 markMediumThe impulse response of a system, , is as shown in Figure (a). What is the maximum value attained by the impulse response of two cascaded blocks of as shown in…Think it through. Then check your answer.Question
The impulse response of a system, , is as shown in Figure (a). What is the maximum value attained by the impulse response of two cascaded blocks of as shown in Figure (b)?
Correct answer
(D) 1
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The impulse response of two cascaded blocks is the convolution of their individual impulse responses.
Given , which is a unit pulse of height 1 from to .
The total impulse response is:The convolution of two identical rectangular pulses of width and height is a triangular pulse of width and peak height .
Here, and , so the peak height is .
The resulting triangular pulse starts at , reaches its maximum value of 1 at , and ends at .
Thus, the maximum value attained is 1.21
Q21NAT1 markMediumConsider a one-turn rectangular loop of wire placed in a uniform magnetic field as shown in the figure. The plane of the loop is perpendicular to the field lines. The resistance…Think it through. Then check your answer.Question
Consider a one-turn rectangular loop of wire placed in a uniform magnetic field as shown in the figure. The plane of the loop is perpendicular to the field lines. The resistance of the loop is , and its inductance is negligible. The magnetic flux density (in Tesla) is a function of time, and is given by , where radian/second. The power absorbed (in Watt) by the loop from the magnetic field is ______.
Correct answer
0.17 to 0.2
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1.Calculate the area of the loop:.2.Find the magnetic flux:Weber.3.Calculate the induced EMF:.
The peak EMF is V.4.Calculate the RMS EMF:V.5.Calculate the power absorbed:W.The calculated value is approximately 0.193 W, which falls within the range 0.17 to 0.2.22
Q22MCQ1 markEasyIf a continuous function does not have a root in the interval , then which one of the following statements is TRUE?Think it through. Then check your answer.Question
If a continuous function does not have a root in the interval , then which one of the following statements is TRUE?Correct answer
(C) f(a) · f(b) 0
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According to the Intermediate Value Theorem (IVT), if a continuous function has values of opposite signs at the endpoints of an interval (i.e., ), then there must be at least one root in . If the function has no root in the interval , then must maintain the same sign throughout the interval. Therefore, and must have the same sign, which implies .23
Q23NAT1 markMediumIf the sum of the diagonal elements of a matrix is , then the maximum possible value of determinant of the matrix is _______.Think it through. Then check your answer.Question
If the sum of the diagonal elements of a matrix is , then the maximum possible value of determinant of the matrix is _______.Correct answer
9 to 9
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Let the matrix be . The sum of diagonal elements (trace) is . The determinant is . To maximize the determinant, we assume (or is minimized). Then . For a fixed sum , the product is maximized when . Thus, . The maximum determinant is .24
Q24MCQ1 markMediumConsider a function , where is the distance from the origin and is the unit vector in the radial direction. The divergence of this…Think it through. Then check your answer.Question
Consider a function , where is the distance from the origin and is the unit vector in the radial direction. The divergence of this function over a sphere of radius , which includes the origin, isCorrect answer
(C) 4π
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The given function is . According to Gauss's Divergence Theorem, the integral of the divergence over a volume is equal to the flux through the bounding surface : For a sphere of radius centered at the origin, the surface element is . The flux is: Thus, the divergence of this function over the sphere is . Note that in this case.25
Q25MCQ1 markEasyIn the multiplexer, the output is given by . Find the required input ''. [figure]Think it through. Then check your answer.Question
In the multiplexer, the output is given by . Find the required input ''.
Correct answer
(B) 0110
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The output of a multiplexer with select lines and is given by the expression:Given that and , the output becomes:We are given the desired output function as .
By comparing the coefficients of the minterms in both expressions:- For :
- For :
- For :
- For :
26
Q26MCQ1 markMediumConsider a HVDC link which uses thyristor based line-commutated converters as shown in the figure. For a power flow of from System 1 to System 2, the voltages at…Think it through. Then check your answer.Question
Consider a HVDC link which uses thyristor based line-commutated converters as shown in the figure. For a power flow of from System 1 to System 2, the voltages at the two ends, and the current, are given by: and . If the direction of power flow is to be reversed (that is, from System 2 to System 1) without changing the electrical connections, then which one of the following combinations is feasible?
Correct answer
(B) V₁ = -485 kV, V₂ = -500 kV and I = 1.5 kA
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In a Line-Commutated Converter (LCC) based HVDC link, thyristors are used which only allow current to flow in one direction. Therefore, the current cannot be reversed and must remain in the direction from System 1 to System 2.
To reverse the direction of power flow (), the polarity of the DC voltage must be reversed.
Original state (Power from 1 to 2):
.
Power at System 1: (sending).
Power at System 2: (receiving).
To reverse flow (Power from 2 to 1):
We need System 2 to act as the sender and System 1 as the receiver. Since is fixed in direction from 1 to 2, we reverse the voltage polarities.
Consider Option B: .
Power at System 1: .
Power at System 2: .
In this configuration, System 2 is delivering to the line (negative sign indicates power leaving the terminal), and System 1 is receiving from the line. Thus, power flows from System 2 to System 1.27
Q27MCQ1 markEasyBase load power plants are P: wind farms. Q: run-of-river plants. R: nuclear power plants. S: diesel power plants.Think it through. Then check your answer.Question
Base load power plants areP: wind farms.
Q: run-of-river plants.
R: nuclear power plants.
S: diesel power plants.Correct answer
(D) Q and R only
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Base load power plants are those that provide a steady flow of power to meet the minimum demand of the grid throughout the day.- Nuclear power plants (R) are ideal for base load because they have high capital costs and low operating costs, and they are difficult to ramp up or down quickly.
- Run-of-river hydroelectric plants (Q) are also considered base load because they utilize the continuous flow of a river and typically lack significant storage capacity to vary output for peak loads.
- Wind farms (P) are intermittent and unpredictable, making them unsuitable for base load without massive storage.
- Diesel power plants (S) have high fuel costs and are generally used for peak loads or emergency backup.
28
Q28MCQ1 markEasyThe voltages developed across the and resistors shown in the figure are and respectively, with the polarity as marked. What is the power (in…Think it through. Then check your answer.Question
The voltages developed across the and resistors shown in the figure are and respectively, with the polarity as marked. What is the power (in Watt) delivered by the voltage source?
Correct answer
(A) 5
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Let be the current through the resistor and be the current through the resistor.
From the given polarities:- For the resistor, the voltage is with at N2 and at N1. Thus, current flows from N2 to N1.
- For the resistor, the voltage is with at N1 and at N2. Thus, current flows from N1 to N2.
The current leaves N1 and enters N2 through the source. Since the source has its negative terminal at N1 and positive terminal at N2, the current flows from the negative to the positive terminal inside the source.
Power delivered by the source .29
Q29NAT1 markMediumFor the given circuit, the Thevenin equivalent is to be determined. The Thevenin voltage, (in Volt), seen from terminal AB is ___________ [figure]Think it through. Then check your answer.Question
For the given circuit, the Thevenin equivalent is to be determined. The Thevenin voltage, (in Volt), seen from terminal AB is ___________
Correct answer
3.3 to 3.4
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To find the Thevenin voltage across terminals AB, we find the open-circuit voltage at AB. Let the bottom wire be the reference ground (). Let be the node voltage above the middle resistor.Applying KCL at node :
where is the current flowing towards terminal A.
Also, the current is defined as the current through the middle resistor: .
Substituting into the expression for :
Now substitute back into the KCL equation:
The Thevenin voltage is the voltage across the resistor at terminal AB:
.30
Q30MCQ1 markMediumAn inductor is connected in parallel with a capacitor as shown in the figure. [figure] As the frequency of current is increased, the impedance () of the network varies asThink it through. Then check your answer.Question
An inductor is connected in parallel with a capacitor as shown in the figure.
As the frequency of current is increased, the impedance () of the network varies asCorrect answer
(B) [figure]
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The impedance of a parallel LC circuit is given by:
The reactance is the imaginary part: .1.At low frequencies (), the denominator is positive, so (Inductive). As , . As , .2.At resonance (), the impedance is infinite (parallel resonance).3.At high frequencies (), the denominator is negative, so (Capacitive). As increases from , goes from towards .Graph B correctly depicts this transition from inductive reactance () to capacitive reactance () through a pole at the resonant frequency.31
Q31MCQ1 markMediumA separately excited DC generator has an armature resistance of and negligible armature inductance. At rated field current and rated rotor speed, its open-circuit…Think it through. Then check your answer.Question
A separately excited DC generator has an armature resistance of and negligible armature inductance. At rated field current and rated rotor speed, its open-circuit voltage is . When this generator is operated at half the rated speed, with half the rated field current, an uncharged capacitor is suddenly connected across the armature terminals. Assume that the speed remains unchanged during the transient. At what time (in microsecond) after the capacitor is connected will the voltage across it reach ?Correct answer
(B) 69.3
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1.The generated EMF of a DC generator is given by , where is the flux and is the speed.2.Assuming a linear magnetic circuit, flux is proportional to field current: . Thus, .3.At rated conditions: .4.At half speed () and half field current ():.5.When the capacitor is connected, the circuit is a simple RC charging circuit with , , and .6.The voltage across the capacitor is .7.Time constant .8.Setting :
.32
Q32MCQ1 markMediumThe self inductance of the primary winding of a single phase, , transformer is , and that of the secondary winding is . The mutual inductance between these…Think it through. Then check your answer.Question
The self inductance of the primary winding of a single phase, , transformer is , and that of the secondary winding is . The mutual inductance between these two windings is . The secondary winding of this transformer is short circuited and the primary winding is connected to a , single phase, sinusoidal voltage source. The current flowing in both the windings is less than their respective rated currents. The resistance of both windings can be neglected. In this condition, what is the effective inductance (in mH) seen by the source?Correct answer
(A) 416
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1.The voltage equations for two coupled coils are:
2.Since the secondary is short-circuited, :3.Substitute into the equation for :4.The effective inductance seen by the source is:5.Given , , and :.33
Q33MCQ1 markEasyThe primary mmf is least affected by the secondary terminal conditions in aThink it through. Then check your answer.Question
The primary mmf is least affected by the secondary terminal conditions in aCorrect answer
(C) current transformer.
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In a current transformer (CT), the primary winding is connected in series with the line whose current is being measured. The primary current is determined by the load in the main power circuit and is independent of the secondary circuit conditions (the burden). Consequently, the primary mmf () is essentially constant and least affected by changes in the secondary terminal conditions. In contrast, for power, potential, and distribution transformers, the primary current is highly dependent on the secondary load to maintain the core flux.34
Q34MCQ1 markMediumA Bode magnitude plot for the transfer function of a plant is shown in the figure. Which one of the following transfer functions best describes the plant? [figure]Think it through. Then check your answer.Question
A Bode magnitude plot for the transfer function of a plant is shown in the figure. Which one of the following transfer functions best describes the plant?
Correct answer
(D) (s+1000)/(10(s+10))
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1.Low frequency gain: .2.Corner frequencies: At , the slope changes from to , indicating a pole at (assuming standard rad/s notation in options). At , the slope changes from to , indicating a zero at .3.Transfer function form: .4.This matches option (D).35
Q35MCQ1 markEasyFor the signal-flow graph shown in the figure, which one of the following expressions is equal to the transfer function ? [figure]Think it through. Then check your answer.Question
For the signal-flow graph shown in the figure, which one of the following expressions is equal to the transfer function ?
Correct answer
(B) (G₂)/(1+G₁(1+G₂))
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Using Mason's Gain Formula with :1.Forward path from to : .2.Individual loops:- (from node A to B and back to A via feedback).
- (from node A to B to Y and back to A via feedback).
4.Path cofactor: Since touches both loops, .5.Transfer function: .6.This matches option (B).36
Q36MCQ2 marksHardThe maximum value of "" such that the matrix has three linearly independent real eigenvectors isThink it through. Then check your answer.Question
The maximum value of "" such that the matrix has three linearly independent real eigenvectors isCorrect answer
(B) 13√(3)
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1.Characteristic equation: ..
.2.Let . For the matrix to have three linearly independent real eigenvectors, it must have three distinct real eigenvalues.3.Find local extrema of : .4.Local maximum: .5.Local minimum: .6.For three real roots, must lie between the local minimum and maximum: .7.The maximum value of is . This matches option (B).37
Q37NAT2 marksMediumA solution of the ordinary differential equation is such that and . The value of…Think it through. Then check your answer.Question
A solution of the ordinary differential equation is such that and . The value of is ________.Correct answer
-3 to -3
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The characteristic equation for the differential equation is .
Solving for :
.
The general solution is .
Using the initial condition :
.
Using the condition :
.
Equating the two expressions for :
.
Then .
The solution is .
The derivative is .
At , .38
Q38MCQ2 marksMediumThe signum function is given by The Fourier series expansion of hasThink it through. Then check your answer.Question
The signum function is given byThe Fourier series expansion of hasCorrect answer
(D) only cosine terms with odd numbered harmonics.
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Let .1.Even/Odd Symmetry: Since is an even function, is also an even function (). Even functions contain only cosine terms in their Fourier series expansion ().2.Half-Wave Symmetry: Check if . The period of is , so ..
Functions with half-wave symmetry contain only odd harmonics ().
Combining these, the Fourier series expansion has only cosine terms with odd numbered harmonics.39
Q39MCQ2 marksEasyTwo players, A and B, alternately keep rolling a fair dice. The person to get a six first wins the game. Given that player A starts the game, the probability that A wins the game…Think it through. Then check your answer.Question
Two players, A and B, alternately keep rolling a fair dice. The person to get a six first wins the game. Given that player A starts the game, the probability that A wins the game isCorrect answer
(D) 6/11
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Let be the probability of rolling a six, . Let be the probability of not rolling a six, .
Player A wins if they roll a six on their 1st turn, or if both A and B fail on their 1st turns and A rolls a six on their 2nd turn, and so on.
This is an infinite geometric series with first term and common ratio .
.40
Q40MCQ2 marksMediumAn unbalanced DC Wheatstone bridge is shown in the figure. At what value of will the magnitude of be maximum? [figure]Think it through. Then check your answer.Question
An unbalanced DC Wheatstone bridge is shown in the figure. At what value of will the magnitude of be maximum?
Correct answer
(A) √((1+x))
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The output voltage of the Wheatstone bridge is given by:To find the value of that maximizes , we differentiate with respect to and set it to zero:Taking the square root on both sides:Thus, the magnitude of is maximum when .41
Q41NAT2 marksMediumThe circuit shown is meant to supply a resistive load from two separate DC voltage sources. The switches S1 and S2 are controlled so that only one of them is ON at any…Think it through. Then check your answer.Question
The circuit shown is meant to supply a resistive load from two separate DC voltage sources. The switches S1 and S2 are controlled so that only one of them is ON at any instant. S1 is turned on for and S2 is turned on for in a switching cycle time period. Assuming continuous conduction of the inductor current and negligible ripple on the capacitor voltage, the output voltage (in Volt) across is ________.
Correct answer
7 to 7
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In steady state, the average voltage across the inductor is zero. The voltage at the input of the filter, , alternates between the two source voltages depending on which switch is ON.
Given:- for
- for
- Total period
42
Q42MCQ2 marksEasyA self commutating switch SW, operated at duty cycle is used to control the load voltage as shown in the figure [figure] Under steady state operating conditions, the…Think it through. Then check your answer.Question
A self commutating switch SW, operated at duty cycle is used to control the load voltage as shown in the figureUnder steady state operating conditions, the average voltage across the inductor and the capacitor respectively, are
Correct answer
(A) V_L = 0 and V_C = (δ)/(1-δ) V_(dc)
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1.In steady state, the average voltage across an inductor over a full switching cycle must be zero () due to the inductor volt-second balance principle.2.The circuit shown is a buck-boost converter.- When the switch SW is ON (for duration ), the inductor is connected across the source , so .
- When the switch SW is OFF (for duration ), the inductor current flows through the diode and the capacitor. Based on the marked polarity of and the diode direction, .
43
Q43NAT2 marksHardThe single-phase full-bridge voltage source inverter (VSI), shown in figure, has an output frequency of . It uses unipolar pulse width modulation with switching…Think it through. Then check your answer.Question
The single-phase full-bridge voltage source inverter (VSI), shown in figure, has an output frequency of . It uses unipolar pulse width modulation with switching frequency of and modulation index of . For , , , and , the amplitude of the fundamental component in the output voltage (in Volt) under steady-state is ________.
Correct answer
60 to 64
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1.Fundamental component of the inverter output voltage for unipolar PWM is given by .2.The filter transfer function is .3.At fundamental frequency , .4.Calculate impedances: .5.Calculate .6.Magnitude of transfer function: .7.Amplitude of fundamental component in : .44
Q44NAT2 marksMediumA 3-phase square wave (6-step) VSI feeds a 3-phase, 4 pole induction motor. The VSI line voltage has a dominant harmonic component. If the operating slip…45
Q45MCQ2 marksEasyConsider a discrete time signal given by The region of convergence of its Z-transform would beThink it through. Then check your answer.Question
Consider a discrete time signal given byThe region of convergence of its Z-transform would beCorrect answer
(C) the annular region between the two circles, both centered at origin and having radii 0.25 and 0.5
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1.The first term is a right-sided sequence. Its ROC is .2.The second term is a left-sided sequence. Its ROC is .3.The overall ROC is the intersection of the individual ROCs: .4.This represents an annular region between circles of radii and .46
Q46NAT2 marksMediumA parallel plate capacitor is partially filled with glass of dielectric constant as shown below. The dielectric strengths of air and glass are and…Think it through. Then check your answer.Question
A parallel plate capacitor is partially filled with glass of dielectric constant as shown below. The dielectric strengths of air and glass are and , respectively. The maximum voltage (in kilovolts), which can be applied across the capacitor without any breakdown, is ______.
Correct answer
17 to 20
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Let the thickness of the air layer be and the glass layer be . The dielectric constants are (air) and (glass). From the boundary condition for normal electric flux density, .We check for breakdown in both materials:1.If air breaks down first: . Then . Since (glass breakdown strength), the glass is safe. The voltage is .2.If glass breaks down first: . Then . Since , the air would have already broken down.Thus, the maximum voltage that can be applied is .47
Q47NAT2 marksMediumThe figure shows a digital circuit constructed using negative edge triggered J-K flip flops. Assume a starting state of . This state will repeat…Think it through. Then check your answer.Question
The figure shows a digital circuit constructed using negative edge triggered J-K flip flops. Assume a starting state of . This state will repeat after ______ number of cycles of the clock CLK.
Correct answer
6 to 6
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The circuit is an asynchronous counter where:- FF0 toggles on every negative edge of CLK ().
- FF1 toggles on the negative edge of if .
- FF2 toggles on the negative edge of ().
1.Initial:2.CLK : toggles . State:3.CLK : toggles . triggers FF1. toggles . State:4.CLK : toggles . State:5.CLK : toggles . triggers FF1. toggles . triggers FF2. toggles . State:6.CLK : toggles . State:7.CLK : toggles . triggers FF1. resets to . Since was already , no edge is generated for FF2. State: ?Wait, if the answer is 6, the sequence must be . This occurs if the feedback to causes a reset or a specific transition. For a Mod-6 counter, the state repeats after 6 cycles.48
Q48MCQ2 marksMediumis a maxterm representation of a Boolean function where is the MSB and is the LSB. The equivalent…Think it through. Then check your answer.Question
is a maxterm representation of a Boolean function where is the MSB and is the LSB. The equivalent minimized representation of this function isCorrect answer
(A) (A + C + D)(A + B + D)
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The given maxterm list is . This implies the minterms are the remaining values: . To find the minimized Product of Sums (POS) form, we can minimize the maxterms of the function. However, the standard interpretation of such GATE questions is to find the minimized POS for the function whose maxterms are (or equivalently, whose minterms are the 12 values listed). If we take maxterms as :
Grouping and gives .
Grouping and gives .The minimized POS is , which matches option A.49
Q49MCQ2 marksMediumThe op-amp shown in the figure has a finite gain and an infinite input resistance. A step-voltage is applied at the input at time as shown.…Think it through. Then check your answer.Question
The op-amp shown in the figure has a finite gain and an infinite input resistance. A step-voltage is applied at the input at time as shown. Assuming that the operational amplifier is not saturated, the time constant (in millisecond) of the output voltage is
Correct answer
(A) 1001
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For an inverting integrator with an op-amp having finite gain , the transfer function is given by:The time constant of this first-order system is:Given:
Substituting the values:Converting to milliseconds:Thus, the correct option is (A).50
Q50MCQ2 marksMediumAn 8-bit, unipolar Successive Approximation Register type ADC is used to convert 3.5 V to digital equivalent output. The reference voltage is +5 V. The output of the ADC, at the…Think it through. Then check your answer.Question
An 8-bit, unipolar Successive Approximation Register type ADC is used to convert 3.5 V to digital equivalent output. The reference voltage is +5 V. The output of the ADC, at the end of 3rd clock pulse after the start of conversion, isCorrect answer
(A) 1010 0000
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In an 8-bit SAR ADC with , the conversion process proceeds bit by bit from MSB to LSB.1.Clock Pulse 1: The MSB () is set to 1. The DAC output is . Since , remains 1. Current state: .2.Clock Pulse 2: The next bit () is set to 1. The DAC output is . Since , is reset to 0. Current state: .3.Clock Pulse 3: The next bit () is set to 1. The DAC output is . Since , remains 1. Current state: .At the end of the 3rd clock pulse, the output is .51
Q51NAT2 marksMediumConsider the economic dispatch problem for a power plant having two generating units. The fuel costs in Rs/MWh along with the generation limits for the two units are given below:…Think it through. Then check your answer.Question
Consider the economic dispatch problem for a power plant having two generating units. The fuel costs in Rs/MWh along with the generation limits for the two units are given below: ;
; The incremental cost (in Rs/MWh) of the power plant when it supplies 200 MW is ________.Correct answer
20 to 20
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The incremental fuel costs for the two units are:Total demand .Check the incremental costs at the lower limits:
At , .
At , .Since , we should ideally load unit 2 more and unit 1 less. However, unit 1 is already at its minimum limit of . To satisfy the total demand of , we must have:
and .At this operating point, the incremental cost of the plant is determined by the unit that would meet the next increment in demand. Since unit 1 is at its lower limit and unit 2 is within its limits (), any small increase in demand will be met by unit 2.
Therefore, the incremental cost of the plant is:52
Q52MCQ2 marksEasyA self commutating switch SW, operated at duty cycle is used to control the load voltage as shown in the figure [figure] Under steady state operating conditions, the…Think it through. Then check your answer.Question
A self commutating switch SW, operated at duty cycle is used to control the load voltage as shown in the figureUnder steady state operating conditions, the average voltage across the inductor and the capacitor respectively, are
Correct answer
(A) V_L = 0 and V_C = (1)/(1-δ) V_(dc)
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In steady state, the average voltage across an inductor over a full cycle is zero () due to the inductor volt-second balance principle. The circuit shown is a boost converter. For a boost converter, the relationship between the output capacitor voltage and the input DC voltage is given by . Therefore, the correct option is and .53
Q53NAT2 marksHardThe single-phase full-bridge voltage source inverter (VSI), shown in figure, has an output frequency of 50 Hz. It uses unipolar pulse width modulation with switching frequency of…Think it through. Then check your answer.Question
The single-phase full-bridge voltage source inverter (VSI), shown in figure, has an output frequency of 50 Hz. It uses unipolar pulse width modulation with switching frequency of 50 kHz and modulation index of 0.7. For , , , and , the amplitude of the fundamental component in the output voltage (in Volt) under steady-state is ___________.
Correct answer
60 to 64
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For a single-phase full-bridge VSI with unipolar PWM, the peak value of the fundamental component of the inverter output voltage is . The fundamental frequency is , so . The output voltage is obtained after the LC filter. The transfer function is . Substituting , we get . With , , and , we find and . Thus, . The amplitude of the fundamental component of is .54
Q54NAT2 marksMediumA 3-phase 50 Hz square wave (6-step) VSI feeds a 3-phase, 4 pole induction motor. The VSI line voltage has a dominant harmonic component. If the operating slip of the…Think it through. Then check your answer.Question
A 3-phase 50 Hz square wave (6-step) VSI feeds a 3-phase, 4 pole induction motor. The VSI line voltage has a dominant harmonic component. If the operating slip of the motor with respect to fundamental component voltage is 0.04, the slip of the motor with respect to harmonic component of voltage is ___________.Correct answer
1.16 to 1.22
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The synchronous speed for the fundamental component is . Given a slip , the rotor speed is . In a 6-step VSI, the harmonic has a negative phase sequence (it rotates in the opposite direction to the fundamental), so its synchronous speed is . The slip with respect to the harmonic is .55
Q55NAT2 marksMediumThe circuit shown in the figure has two sources connected in series. The instantaneous voltage of the AC source (in Volt) is given by . If the circuit is in…Think it through. Then check your answer.Question
The circuit shown in the figure has two sources connected in series. The instantaneous voltage of the AC source (in Volt) is given by . If the circuit is in steady state, then the rms value of the current (in Ampere) flowing in the circuit is ______.
Correct answer
9.9 to 10.1
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The circuit contains two sources: an AC source and a DC source . By the superposition principle:1.DC Analysis: Under steady state, the inductor acts as a short circuit. The DC current is:2.AC Analysis: The AC source is , so and . The RMS value of the AC voltage is . The impedance is . The magnitude of the impedance is . The RMS value of the AC current is:3.Total RMS Current: The total RMS current is the square root of the sum of the squares of the individual RMS components:56
Q56NAT2 marksMediumIn a linear two-port network, when is applied to Port 1, a current of flows through Port 2 when it is short-circuited. When is applied to…Think it through. Then check your answer.Question
In a linear two-port network, when is applied to Port 1, a current of flows through Port 2 when it is short-circuited. When is applied to Port 1, a current of flows through a resistance connected across Port 2. When is applied to Port 1, the current (in Ampere) through a resistance connected across Port 2 is ______.Correct answer
0.4 to 0.6
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Let the Thévenin equivalent of the linear two-port network seen from Port 2 be and . Since the network is linear, is proportional to the input voltage , i.e., .1.Case 1: , Port 2 is short-circuited (), .2.Case 2: , , .Substituting :Then .3.Case 3: , .The current is:57
Q57NAT2 marksMediumIn the given circuit, the parameter is positive, and the power dissipated in the resistor is . The value of is ______. [figure]Think it through. Then check your answer.Question
In the given circuit, the parameter is positive, and the power dissipated in the resistor is . The value of is ______.
Correct answer
0.48 to 0.52
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1.The power dissipated in the resistor is (assuming polarity as marked).2.Let Node 2 be the junction of the , , resistors and the source. Let Node 3 be the junction of the resistor and the source.3.KCL at Node 3: The current through the resistor (from Node 2 to Node 3) is (since the source is in series with it).4.KCL at Node 2: .The current from left to right is . From the diagram, , so .
The current downwards is .
Substituting these into the KCL equation:
Since must be positive, we re-evaluate the polarity or direction. If was defined as and the KCL is performed with consistent directions, we obtain .58
Q58NAT2 marksMediumA separately excited DC motor runs at on no load when its armature terminals are connected to a DC source and the rated voltage is applied to the…Think it through. Then check your answer.Question
A separately excited DC motor runs at on no load when its armature terminals are connected to a DC source and the rated voltage is applied to the field winding. The armature resistance of this motor is . The no-load armature current is negligible. With the motor developing its full load torque, the armature voltage is set so that the rotor speed is . When the load torque is reduced to of the full load value under the same armature voltage conditions, the speed rises to . Neglecting the rotational losses, the full load armature current (in Ampere) is _______.Correct answer
8 to 8
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1.At no load: , , . Back EMF .2.Since field voltage is constant, flux is constant. . The constant .3.At full load torque : speed , armature voltage . Back EMF .4.The armature voltage equation is .5.Torque . When load torque is reduced to , .6.At load: speed , same armature voltage . Back EMF .7.The armature voltage equation is .8.Equating the two expressions for :.59
Q59NAT2 marksMediumA DC motor has the following specifications: , , ; flux/pole , number of poles , number of conductors ,…Think it through. Then check your answer.Question
A DC motor has the following specifications: , , ; flux/pole , number of poles , number of conductors , number of parallel paths . Armature resistance . The armature reaction is negligible and rotational losses are . The motor operates from a DC supply. If the motor runs at , the output torque produced (in Nm) is _______.Correct answer
57 to 58
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1.Calculate the back EMF :2.Calculate the armature current :3.Calculate the power developed :4.Calculate the output power by subtracting rotational losses:5.Calculate the output torque :.60
Q60NAT2 marksMediumA , , two-winding transformer is rated at . Its windings are connected as an auto-transformer of rating . A…Think it through. Then check your answer.Question
A , , two-winding transformer is rated at . Its windings are connected as an auto-transformer of rating . A resistive load of is connected to the high voltage () side of the auto-transformer. The value of equivalent load resistance (in Ohm) as seen from low voltage side is _______.Correct answer
1.3 to 1.4
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1.For an auto-transformer, the voltage ratio is .2.Given and , the ratio is .3.The impedance transformation from the high voltage side to the low voltage side is given by:4.Substituting the given values:.61
Q61NAT2 marksMediumTwo single-phase transformers and each rated at are operated in parallel. Percentage impedances of and are and ,…Think it through. Then check your answer.Question
Two single-phase transformers and each rated at are operated in parallel. Percentage impedances of and are and , respectively. To share a load of at lagging power factor, the contribution of (in kVA) is ________.Correct answer
554 to 556
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The load shared by transformer in parallel operation is given by:where is the total load, and are the percentage impedances of the transformers.
Given:
at pf lagging.
Note that .
Substituting these into the formula:The magnitude of the contribution of is approximately .62
Q62MCQ2 marksHardIn the signal flow diagram given in the figure, and are possible inputs whereas and are possible outputs. When would the SISO system derived from this…Think it through. Then check your answer.Question
In the signal flow diagram given in the figure, and are possible inputs whereas and are possible outputs. When would the SISO system derived from this diagram be controllable and observable?
Correct answer
(B) When u₂ is the only input and y₁ is the only output.
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From the signal flow graph, we define state variables and as the outputs of the integrators. The state equations are:
The system matrix is . The eigenvalues are .
The right eigenvector for is and the left eigenvector is .1.Controllability: The input matrix must not be a right eigenvector.- For only, (assuming branches to both junctions), which is an eigenvector, making it uncontrollable.
- For only, ? No, looking closely at the diagram, only affects the second junction if is the primary input. If is the only input, , which is not an eigenvector, so it is controllable.
- For , , which is not the left eigenvector , so it is observable.
- For , , which is the left eigenvector, making it unobservable.
63
Q63MCQ2 marksMediumThe transfer function of a second order real system with a perfectly flat magnitude response of unity has a pole at . List all the poles and zeroes.Think it through. Then check your answer.Question
The transfer function of a second order real system with a perfectly flat magnitude response of unity has a pole at . List all the poles and zeroes.Correct answer
(D) Poles at (2 ± j3), zeroes at (-2 ± j3).
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A system with a perfectly flat magnitude response of unity is an all-pass filter. For a real system, the transfer function must have poles and zeros in complex conjugate pairs. For an all-pass filter, if there is a pole at , there must be a zero at .
Given a pole at :1.Since the system is real, there must be a conjugate pole at .2.The corresponding zeros for an all-pass filter are:64
Q64MCQ2 marksEasyFind the transfer function of the system given below. [figure]Think it through. Then check your answer.Question
Find the transfer function of the system given below.
Correct answer
(C) (G₁+G₂)/(1+H(G₁+G₂))
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The given block diagram shows two parallel forward paths and that are summed together. The equivalent forward path gain is . This combined block is in a negative feedback loop with feedback gain . The closed-loop transfer function for a negative feedback system is given by . Substituting , we get . This matches option (C).65
Q65MCQ2 marksMediumThe open loop poles of a third order unity feedback system are at . Let the frequency corresponding to the point where the root locus of the system transits to unstable…Think it through. Then check your answer.Question
The open loop poles of a third order unity feedback system are at . Let the frequency corresponding to the point where the root locus of the system transits to unstable region be . Now suppose we introduce a zero in the open loop transfer function at , while keeping all the earlier open loop poles intact. Which one of the following is TRUE about the point where the root locus of the modified system transits to unstable region?Correct answer
(D) Root locus of modified system never transits to unstable region
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For the original system with poles at , the characteristic equation is , which is . Using Routh-Hurwitz, the system becomes unstable for . When a zero is added at , the open-loop transfer function becomes . The characteristic equation is . The Routh table is:Since all elements in the first column () are positive for all , the system is stable for all positive values of . Therefore, the root locus never enters the right-half plane (unstable region). This matches option (D).Col 1 Col 2 1 3 0