A linear resistive circuit contains two independent voltage sources, V1 = 20 V and V2 = 12 V. With both sources on, the current through the load resistor is I = 14.5 mA. With V2 switched off (replaced by a short circuit) and V1 unchanged, the load current is −5.5 mA. Find the load current I when V1 is switched off and only V2 = 12 V is active.
Superposition worksheet with answers
1.Easy
I = 14.5 mA (both sources)I = −5.5 mA (only V1)
I = mA
2.Easy
Use superposition to find the contribution IR1′ of V1 alone to the current IR1 through R1 in the direction of the arrow.
V1 = 12 VV2 = 20 VR1 = 4 ΩR2 = 12 ΩR3 = 3 Ω
IR1′ = A
3.Medium
Use superposition to find the current IR2 through R2 in the direction of the arrow.
V1 = 10 VIs = 2 AR1 = 20 ΩR2 = 2 ΩR3 = 20 ΩR4 = 10 Ω
IR2 = A
4.Medium
A linear resistive circuit contains one voltage source Vs and one current source Is. The current I through a load resistor is measured twice: with Vs = 12 V and Is = 2 mA, I = 7.4 mA; with Vs = 8 V and Is = 5 mA, I = 5.3 mA. Find the load current I when Vs = 12 V and Is = 3 mA.
12 V, 2 mA → 7.4 mA8 V, 5 mA → 5.3 mAVs = 12 V, Is = 3 mA
I = mA
5.Hard
Use superposition to find the voltage VR3 across R3 with the polarity shown.
V1 = 10 VIs = 0.5 AV2 = 36 VR1 = 15 ΩR2 = 20 ΩR3 = 20 ΩR4 = 15 Ω
VR3 = V
6.Hard
Use superposition to find the power PR2 absorbed by R2.
V1 = 5 VIs = 6 AV2 = 36 VR1 = 3 ΩR2 = 8 ΩR3 = 25 ΩR4 = 25 Ω
PR2 = W
Answer key
- 1. I = 20 mA
- 2. IR1′ = 1.875 A
- 3. IR2 = −0.1429 A
- 4. I = 7.5 mA
- 5. VR3 = −1.016 V
- 6. PR2 = 207.1 W
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