UPSC Civil Services (Main) Examination 2026 — Electrical Engineering Optional Paper I: Question Paper

07 Sep UPSC Civil Services (Main) Examination 2026 — Electrical Engineering Optional Paper I: Question Paper | Plutus IAS

Posted at 07 Sep 2026 in UPSC by Tushar 0 Comments

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The questions below are from Electrical Engineering Optional Paper I of UPSC Civil Services (Main) Examination 2026 (held 2026-08-30) — the actual paper, which is public government content. This page carries the questions for reference and revision; model answers for this paper are not published here.

Official paper (PDF): upsc.gov.in.

The value of the integral $\int_{-\infty}^{\infty}X(\omega)d\omega$
The value of the integral $\int_{-\infty}^{\infty}|X(\omega)|^2 d\omega$
Calculate the voltage across the SCR at the instant SCR is triggered.
Find the voltage that appears across the SCR when current decays to zero.
Find the peak inverse voltage for the SCR. 10 $$I_{fd \text{ max}} = \left[ \frac{V_s}{4R} \left( 1 – \frac{E}{V_s} \right)^2 \right]$$ For a type-A chopper feeding an R-L-E load, show that the maximum value of average current rating for the freewheeling diode, in case the load current remains continuous, is given by $$I_{fd \text{ max}} = \left[ \frac{V_s}{4R} \left( 1 – \frac{E}{V_s} \right)^2 \right]$$ where $V_s$ is the input voltage to the chopper. 10 KVMS-P-ETG/13 16 ![img-34.jpeg](img-34.jpeg) The signal m(t) shown in the following figure is used once to frequency modulate a carrier and once to phase modulate the same carrier : ![img-35.jpeg](img-35.jpeg) Find the relation between $k_p$ and $k_f$ such that the maximum phase of the modulated signal in both the cases is equal, where $k_p$ and $k_f$ are phase and frequency sensitivities, respectively of the modulator. 10 KVMS-P-ETG/13 17 [P.T.O. A 6.6 kV, three-phase, star-connected, cylindrical rotor alternator develops rated voltage with field current of 5 A on open circuit. It takes 100 A armature current at 0.2 p.f. lag for 1.0 A field current with its armature symmetrically shorted, all at rated speed. The alternator is delivering maximum power at rated speed to 6.6 kV bus with a field current of 4.5 A. Find the (i) power generated and delivered by the alternator, (ii) load angle and (iii) power factor and reactive power of the alternator. Assume linear magnetic circuit. 20 A 240 V, 1200 r.p.m., 15 A, separately excited DC motor has armature resistance of 1.0 Ω. The motor is operated under dynamic braking with chopper control. The braking resistance has a value of 20 Ω.
Calculate the duty ratio of the chopper for the motor speed of 1000 r.p.m. and braking torque equal to 1.5 times the rated motor torque.
What will be the motor speed for the duty ratio of 0.5 and motor torque equal to its rated torque? 10 A 200 V, 875 r.p.m., 150 A, separately excited DC motor has an armature resistance of 0.06 Ω. It is fed from a single-phase fully controlled rectifier with an AC source voltage of 230 V, 50 Hz. Assuming the continuous conduction, calculate the—
firing angle (α) for rated motor torque and 750 r.p.m.;
firing angle for rated motor torque and (-500) r.p.m.;
motor speed for α = 160° and rated torque. 10 KVMS-P-ETG/13 18 An FM signal with a frequency deviation of 15 kHz at a modulation frequency of 5 kHz is applied to two frequency multipliers connected in cascade. The first multiplier multiplies the frequency by 1.5 times and the second multiplier multiplies it by 4 times. Determine the frequency deviation and the modulation index of the FM signal obtained at second multiplier output. Also compute the approximate bandwidth of the FM signal. 10 ★★★ KVMS-P-ETG/13 19 SB27—354

Questions reproduced from the official paper for study purposes; verify on the exam-conducting body’s official website.