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GATE 2025 BM – Question 40

Electrical Circuits · AC Circuits and Resonance · 2 marks · Multiple choice

Vin=10cos(1000t) V drives the shown 3 kΩ resistor in series with a parallel 1 kΩ–1 μF branch. Find input-impedance magnitude in kΩ to one decimal place.

Diagram for GATE 2025 BM question 40
  1. 5.0
  2. 3.5
  3. 6.0
  4. 4.5

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Show answer and explanation

Correct answer: (B) 3.5

Explanation

At ω=1000 rad/s, capacitor impedance is −j1000 Ω. In parallel with 1000 Ω, its equivalent is 1000/(1+j)=500−j500 Ω. Adding the series resistor yields 3500−j500 Ω. Magnitude is √(3500²+500²)≈3535.5 Ω=3.5 kΩ to one decimal, B.

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