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UPSC Electrical Engineering — Previous Year Questions

Every question from Electrical Engineering papers in UPSC Civil Services Mains (2021–2026), organised by year. 96 questions in total, each with directive-word analysis, model answer points, and a full evaluation rubric.

96Questions
6Years covered

2026 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2026

Paper I

  1. Q1 (a) For the circuit shown below, if the power loss in 1 Ω resistor is 16 W, find the value of k in the dependent source… 50 marks
  2. Q2 (a) (i) Find the values of R and C in the figure shown below, so that V_b = 3V_a, also V̄_b and V̄_a are in quadrature… 50 marks
  3. Q3 (a) (i) For the circuit shown below, steady state is achieved with switch K open. At t = 0, switch K is closed. Find… 50 marks
  4. Q4 (a) (i) The continuous-time signal x(t) = cos(20πt + π/4) is ideally sampled at a rate of 30 samples per second. The… 50 marks
  5. Q5 (a) For the circuit given in the figure below, the input voltage signal is given by V_in = 1·5 sin 62·8t + 0·5 sin… 50 marks
  6. Q6 (a) Design a MOD-6 synchronous DOWN counter using J-K flip-flops. (20 marks) (b) A three-phase, star-connected, 415 V… 50 marks
  7. Q7 (a) Design a Programmable Logic Array (PLA) for a combinational logic circuit that computes the square of 3-bit binary… 50 marks
  8. Q8 (a) A 6·6 kV, three-phase, star-connected, cylindrical-rotor alternator develops rated voltage on open circuit with a… 50 marks

Paper II

  1. Q1 (a) A unity feedback system has open loop transfer function G(s) = K/(s(s+q)). Evaluate the value of K and q so that… 50 marks
  2. Q2 (a) Determine the response of the system shown in the following figure when it is excited by a unit step input. (20… 50 marks
  3. Q3 (a) (i) A system has a unit response as c(t) = 1 − e^(−0·5t). Evaluate its unit impulse and unit ramp response… 50 marks
  4. Q4 (a) Design a PI controller so that a unity feedback system having open loop transfer function G(s)H(s) = 10 / ((s + 2)… 50 marks
  5. Q5 (a) Write the state space equation for the following circuit. [Circuit diagram: voltage source V(t), series resistance… 50 marks
  6. Q6 (a) Determine the efficiency of a 400 km long transmission line delivering 100 MW load at 240 kV, 0·85 lagging p.f. at… 50 marks
  7. Q7 (a) A 3-phase line is terminated by a star-connected resistive load of 800 ohm per phase. The line conductors are… 50 marks
  8. Q8 (a) A hollow cylinder made of insulating material surrounded by a thin metal sheath has inner and outer diameters of 4… 50 marks

2025 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2025

Paper I

  1. Q1 (a) In the circuit given below, find the voltages at point A and point B. 10 marks (b) Determine the time domain signal… 50 marks
  2. Q2 (a) In the circuit shown in the diagram, initially key K₁ is closed and capacitor has no charge (at time t = 0). Now at… 50 marks
  3. Q3 (a) Consider the Boolean function: F(A, B, C, D) = Σ m (1, 3, 4, 11, 12, 13, 14, 15). Implement it with a 4-to-1… 50 marks
  4. Q4 (a) For the Schottky transistor circuit shown below, determine I_B, I_D, I_C and V_CE. Next, remove the Schottky diode… 50 marks
  5. Q5 (a) As shown in the figure, just inside the surface of a dielectric slab, the electric field (E₁) is 15 V/m and it… 50 marks
  6. Q6 (a) (i) What is meant by armature reaction in DC machines ? Show with the help of developed view of armature conductors… 50 marks
  7. Q7 (a) It is given that E⃗ = Eₘ sin (ω t - α z) â_y in free space α > 0. (i) Determine D⃗, B⃗ and H⃗. Plot E⃗ and H⃗ at t… 50 marks
  8. Q8 (a) (i) Show that the Smith chart constructed for a lossless transmission line gives a family of r-circles, having a… 50 marks

Paper II

  1. Q1 (a) The block diagram of a system is as shown below : Evaluate the overall transfer function (Y(s))/(R(s)) using block… 50 marks
  2. Q2 (a) An LTI system with the following state-space representation is given : ẋ = [0 1] x + [0] u [0 -0.5] [k] y = [1 0] x… 50 marks
  3. Q3 (a) (i) Sketch the approximate root locus plot for a time-delay system approximated by the transfer function G(s) =… 50 marks
  4. Q4 (a) (i) Consider a second-order type-1 system with no zeros. The system under unity feedback admits a resonant peak of… 50 marks
  5. Q5 (a) Given a second-order linear time-invariant system G(s) with a relative degree of 2. G(s) admits a zero steady-state… 50 marks
  6. Q6 (a) Determine the sending-end voltage, current, power factor of a single-phase, 50 Hz, 76·2 kV transmission line… 50 marks
  7. Q7 (a) Two generators are connected in parallel to the low-voltage side of a 3-phase, Δ-Y transformer as shown below … 50 marks
  8. Q8 (a) The figure below shows the single-line diagram of a generator connected through parallel transmission lines to an… 50 marks

2024 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2024

Paper I

  1. Q1 (a) Find the voltage on points A and B of the given circuit : (10 marks) (b) Determine the Z-transform of x[n] =… 50 marks
  2. Q2 (a) Draw the circuit diagram, function table, logic symbol and switch model for a CMOS gate (using six transistors)… 50 marks
  3. Q3 (a) Determine the time signal that corresponds to the following bilateral Laplace transform and the ROCs given below by… 50 marks
  4. Q4 (a) In the circuit diagram given here, load resistance R_L is to be set for maximum power transfer. Draw Thevenin… 50 marks
  5. Q5 (a) A uniform plane wave travels in vacuum along +y direction. The electric field of the wave at some instant is given… 50 marks
  6. Q6 (a) (i) An AM signal s(t) = A_c[1 + kₐ m(t)]cos(2πf_c t) is applied to the system shown in the figure. Show that the… 50 marks
  7. Q7 (a) (i) Draw the neat and properly labelled output voltage waveform of a three-phase, phase-controlled rectifier having… 50 marks
  8. Q8 (a) In the figure given below, region 1 is the side of the plane y+z=1 containing the origin and in this region, μᵣ₁ =… 50 marks

Paper II

  1. Q1 (a) What are the limitations of (i) Proportional (P), (ii) Integral (I), (iii) Derivative (D), and (iv) PID… 50 marks
  2. Q2 (a) The open-loop transfer function of a feedback control system incorporating a dead time element is given by: G(s) =… 50 marks
  3. Q3 (a) An underdamped second order system having a transfer function of the form M(s) = (Kωₙ²)/(s² + 2ξωₙ s + ωₙ²) has a… 50 marks
  4. Q4 (a) The capacitance of a piezoelectric transducer is 2000 pF and charge sensitivity is 30 × 10⁻³ C/m. Assume the… 50 marks
  5. Q5 (a) The block diagram of a position control system is shown in the figure. Determine the sensitivity of the closed loop… 50 marks
  6. Q6 (a) Calculate the power loss in the transmission system given in the following figure. The numerical values of… 50 marks
  7. Q7 (a) Calculate the real and reactive power at sending end of a transmission line while delivering 10 MVA load at 0·85… 50 marks
  8. Q8 (a) Two sources M1 and M2 emit messages x1, x2, x3 and y1, y2, y3 with the joint probability P(X, Y) as shown below in… 50 marks

2023 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2023

Paper I

  1. Q1 (a) Obtain Norton equivalent circuit at terminals ab of the coupled circuit shown in the figure. Using it, find out the… 50 marks
  2. Q2 (a) For the circuit shown in the figure, obtain the value of voltage across 0·5 Ω and 2·5 Ω resistors using nodal… 50 marks
  3. Q3 (a) (i) Consider the shift register shown in the figure below, which is implemented using D flip-flops and 2 : 1… 50 marks
  4. Q4 (a) For the circuit shown below, early voltage V_A = ∞ and β = 100. Find the reverse saturation current if: (i) the… 50 marks
  5. Q5 (a) A 400 V, 50 Hz, 3-phase star-connected cylindrical rotor synchronous motor has synchronous impedance of (0·5 + j… 50 marks
  6. Q6 (a) A 200 V, 1100 rpm, dc shunt motor takes 1·5 A and runs at 1150 rpm under no load condition at rated voltage. Its… 50 marks
  7. Q7 (a) A 400 V, 3-phase, 50 Hz, star-connected synchronous motor has per phase synchronous impedance Zₛ = (0·5 + j 3·5) Ω… 50 marks
  8. Q8 (a) A 415 V, 4-pole, 3-phase, 50 Hz, star-connected squirrel cage induction motor has per phase parameters of r_s = 1·1… 50 marks

Paper II

  1. Q1 (a) The figure shows a unity feedback system with open-loop transfer function G(s) = K/((s + 1)(s + 2)). The… 50 marks
  2. Q2 (a) The block diagram of a feedback system is shown in the figure: the forward path is G(s) = K/((s − 1)(s² + 4s + 7))… 50 marks
  3. Q3 (a) Write the state and output equations for the system shown in the figure. Choose state variables x₁ and x₂ as shown… 50 marks
  4. Q4 (a) Consider a systematic linear block code with binary elements whose parity check equations are p₁ = m₁ + m₂ + m₃ p₂… 50 marks
  5. Q5 (a) The figure shows a compensator network, where R₁ = 3 MΩ, R₂ = 1 MΩ, C = 1 μF. Vᵢ(t) and Vₒ(t) are the input voltage… 50 marks
  6. Q6 (a) (i) A power system has two generators with the following cost curves : Generator 1 : C₁(P_g1) = 0.008 P_g1² + 8… 50 marks
  7. Q7 (a) A discrete memoryless source generates three independent message symbols m_1, m_2 and m_3 with probabilities 0·9… 50 marks
  8. Q8 (a) The figure shows a unity feedback system with G(s) = 2/[s(s+1)(s+2)(s+3)]. (i) Sketch the approximate polar plot of… 50 marks

2022 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2022

Paper I

  1. Q1 (a) For the circuit shown in Figure 1(a), find the V_in, V_S and power supplied by the dependent source. (10 marks) (b)… 50 marks
  2. Q2 (a) (i) For the circuit shown in Figure 2(a)(i), initial current through the coil is zero. The switch is closed at time… 50 marks
  3. Q3 A common-emitter amplifier circuit is shown in Figure 3(a). Neglect r_x and r_o and assume the current source to be… 50 marks
  4. Q4 For the network shown in Figure 4(a)(i) and its excitation function shown in Figure 4(a)(ii), find the response v(t)… 50 marks
  5. Q5 (a) The diagram of Master-Slave S-R flip-flop and the waveform applied to the Master flip-flop is shown in Figure 5(a)… 50 marks
  6. Q6 (a) The plane wave E = 30 cos (ωt – z) aₓ V/m in air normally hits a lossless medium (μ = μ₀, ε = 4ε₀) at z = 0. (i)… 50 marks
  7. Q7 (a) A three-phase, 5 kW, 440 V, 6 pole, star connected synchronous motor having negligible stator resistance and… 50 marks
  8. Q8 (a) (i) Differentiate between the functions of Decade counter and BCD counter with example. (10 marks) (ii) Draw the… 50 marks

Paper II

  1. Q1 (a) A closed-loop system is shown in the figure below. The maximum overshoot for the system is 40% and the peak time is… 50 marks
  2. Q2 (a) A unity feedback system is shown in the figure below. Determine the range of α for which the system is stable and… 50 marks
  3. Q3 (a) (i) The figure below shows a schematic diagram of shunt ohmmeter. It consists of a battery in series with an… 50 marks
  4. Q4 (a) (i) List various interrupts in microprocessor 8085 in order of decreasing priority. Specify which of these are… 50 marks
  5. Q5 (a) Determine the inductance of a single-phase transmission line consisting of three conductors of 2 cm radii in the… 50 marks
  6. Q6 (a) A three-phase, 50 Hz transmission line is 400 km long. The voltage at the sending end is 220 kV. The line… 50 marks
  7. Q7 (a) The figure below shows the encoder for a rate r = 1/2, constraint length k = 4 convolutional code : [Figure: input… 50 marks
  8. Q8 (a) Answer the following : (i) Write the recommended expression for time-current relationship of standard IDMT relay… 50 marks

2021 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2021

Paper I

  1. Q1 (a) In Figure 1(a) shown below, the two-port network is characterized in terms of y-parameters with y₁₁ = 3·3 × 10⁻³ S… 50 marks
  2. Q2 (a) Find the Thevenin's equivalent of the circuit shown in Figure 2(a) below as seen from the load impedance Z_L. Also… 50 marks
  3. Q3 (a) (i) Explain what happens when a circuit shown in Figure 3(a)(i) below is constructed using logarithmic amplifier… 50 marks
  4. Q4 (a) Consider a discrete time system with transfer function given by H(z) = Y(z)/R(z) = (z⁻¹ - ½z⁻²)/(1 - z⁻¹ + 2/9… 50 marks
  5. Q5 (a) A step down dc chopper is feeding a load of R = 10 Ω and L = 20 mH. The dc supply voltage is 100 V. The chopper is… 50 marks
  6. Q6 (a) The magnetic field intensity of a linearly polarized uniform plane wave propagating in the +Y-direction in sea… 50 marks
  7. Q7 The following test data are obtained for a three-phase, 195 MVA, 15 kV, 50 Hz star connected synchronous machine. Open… 50 marks
  8. Q8 For an FM communication system with β = 2 and white channel noise with PSD Sₙ(ω) = 10⁻¹⁰, the output SNR is found to be… 50 marks

Paper II

  1. Q1 (a) A system is described by the following state equations : dotx₁ = x₁ + x₂ + 3x₃ dotx₂ = 2x₁ + 3x₂ + u₁ dotx₃ = 2x₂ +… 50 marks
  2. Q2 (a) Draw the sequence networks and calculate the load sequence impedances of a load circuit as shown in figure. The… 50 marks
  3. Q3 3.(a) A solidly earthed 400 KV, 3 phase busbar system is connected with two incoming and four outgoing lines (feeders)… 50 marks
  4. Q4 4.(a)(i) The configuration of a 400 KV 3 phase line is shown in figure. The radius of each sub-conductor is 2 cm… 50 marks
  5. Q5 (a) Explain the ratio error and phase angle error of current transformer. 10 marks (b) The two top rows of a Routh… 50 marks
  6. Q6 (a) A synchronous machine is connected to an infinite bus through a transformer and a double circuit line as shown in… 50 marks
  7. Q7 (a) Discuss the percentage differential Relay with harmonic restraint with the help of diagram and also draw the… 50 marks
  8. Q8 (a)(i) Prove that the minimum distance of any linear (n, k) block code satisfies dmin ≤ 1 + n – k. (5 marks) (a)(ii)… 50 marks

How Electrical Engineering answers are marked

The shape the examiner expects, what earns the marks and the traps that lose them: the same card our rubrics for this subject are written from.

Answer skeleton

  1. Circuit or model
  2. Assumptions
  3. Analysis
  4. Result and interpretation

What earns the marks

  • Redraw the circuit or equivalent model first
  • Mark polarities and reference directions
  • Use per-unit where the problem invites it
  • Comment on stability, regulation or response

What earns the extra mark

  • Phasor diagram
  • Block diagram

Traps that cost marks

  • Formula application without the equivalent circuit
  • Sign errors
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