36 solved GATE EE questions on Electrical & Electronic Measurements, drawn from 12 exam years and grouped by year. Every question shows the official answer and a step-by-step solution.
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Distinguish instrument accuracy, precision, and resolution before trusting a reading. These selected foundations connect bridge circuits, instrument transformers, error analysis, and digital measurement principles through original analytical exercises. State the instrument class and full-scale range before computing errors.
Our study notes and original examples support the PYQs below; they are not official exam questions or a replacement for the current syllabus.
Accuracy class specifies the maximum error as a percentage of full-scale deflection, not of the reading. The percentage error referred to the actual reading increases as the reading decreases below full scale. Systematic errors can be corrected; random errors are reduced by averaging repeated measurements.
Check yourself: Are you expressing the error as a percentage of the reading or of full scale?
At balance, R₁R₄ = R₂R₃ and no current flows through the galvanometer. Sensitivity depends on the supply voltage and the galvanometer's current responsivity. For AC bridges (Maxwell, Schering, Wien), both magnitude and phase balance conditions must be satisfied simultaneously.
Check yourself: Have you verified both the resistive and reactive balance conditions for an AC bridge?
A current transformer (CT) steps down line current for ammeter measurement; its secondary must never be open-circuited under load, as dangerously high voltages can develop. A potential transformer (PT) steps down high voltage for voltmeter measurement. Ratio and phase-angle errors arise from magnetising current and core losses.
Check yourself: Is the CT secondary properly short-circuited or connected to its burden before primary energisation?
A PMMC (permanent-magnet moving-coil) instrument responds to the average value of current; it reads correctly only for DC or known waveforms. A moving-iron instrument responds to the RMS value and works on both AC and DC. The deflecting torque, controlling torque, and damping mechanism determine steady-state accuracy and response time.
Check yourself: Is the instrument type suited to the signal: DC-only (PMMC) or AC/DC (moving-iron)?
A digital voltmeter converts an analogue input to a digital display. Resolution is determined by the number of counts (e.g. a 3½-digit meter has 2000 counts, resolving 1 part in 2000). Quantisation error is at most ±½ of the least significant digit. Accuracy includes both quantisation and analogue-circuit errors.
Check yourself: Does the number of display digits match the resolution you assumed?
Original teaching example · not a PYQ
Original mini-example: in a balanced Wheatstone bridge, R₁ = 100 Ω, R₂ = 200 Ω, and R₃ = 150 Ω. Find the unknown resistance R₄. If each of the three known resistors has a tolerance of ±0.5%, estimate the maximum percentage error in the calculated value of R₄.
R₄ = 300 Ω with a maximum percentage error of ±1.5%.
A PMMC ammeter has a full-scale deflection current of 1 mA and an internal resistance of 50 Ω. What shunt resistance is needed to extend its range to 100 mA?
R_shunt = 50/99 Ω ≈ 0.505 Ω.
At full-scale deflection, the voltage across the meter is 1 mA × 50 Ω = 50 mV. The shunt must carry the remaining 99 mA at the same voltage: R_shunt = 50 mV / 99 mA = 50/99 Ω. Equivalently, using the multiplying factor n = 100: R_shunt = R_m/(n − 1) = 50/99 Ω.
Supplemental reading, not an official GATE reading list or an endorsement of these notes.
Freely accessible textbook covering DC and AC measurement principles, bridge circuits, instrument types, and error analysis with interactive examples.
This page shows 36 recent questions from the released archive, newest first. For older questions and complete papers, browse all GATE EE papers. Questions can carry more than one subject tag; counts are not marks weightage.
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