RC & RL transients worksheet with answers

Free printable RC & RL transients worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

The capacitor is uncharged when the switch closes at t = 0. Find the charging current i at t = 300 ms.

V_s = 24 VR = 4.7 kΩC = 220 µFt = 300 ms

i = mA

2.Easy

The capacitor is uncharged when the switch closes at t = 0. Find the capacitor voltage v_C at t = 750 ms.

V_s = 20 VR = 10 kΩC = 220 µFt = 750 ms

v_C = V

3.Medium

The inductor carries no current before the switch closes at t = 0. Find the energy W(∞) stored in the inductor once the circuit has settled, in mJ.

V_s = 15 VR = 10 ΩL = 150 mH

W(∞) = mJ

4.Medium

The source Vₛ charges the capacitor through R₁, and R₂ is connected in parallel with C. The capacitor is uncharged when the switch closes at t = 0. Find the time constant τ of the circuit after the switch closes.

V_s = 24 VR₁ = 3.3 kΩR₂ = 1 kΩC = 100 µF

τ = ms

5.Hard

Just before the switch closes at t = 0, the capacitor holds 6 V with the polarity shown. How long does it take for v_C to reach 10.5 V? Find t.

V_s = 15 VR = 1 kΩC = 100 µFv_C(0) = 6 V

t = ms

6.Hard

A timer starts charging an uncharged capacitor through a resistor from a 15 V supply at t = 0. It must trigger when the capacitor voltage reaches 9.48 V, exactly 100 ms after the start. With R = 4.7 kΩ, find the capacitance C needed.

V_s = 15 VV_th = 9.48 VT = 100 msR = 4.7 kΩ

C = µF

Answer key

1. i = 3.82 mA
2. v_C = 5.778 V
3. W(∞) = 168.8 mJ
4. τ = 76.74 ms
5. t = 69.31 ms
6. C = 21.28 µF

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