How to use the Superposition Theorem Calculator
- 1. Enter source 1V1 with its series resistor R1.
- 2. Enter source 2A voltage source with R2, or a current source.
- 3. Get every caseVA, I3 and branch currents for each source and the total.
How superposition works
In a linear circuit with several independent sources, any voltage or current equals the sum of the values caused by each source acting alone. To turn a source off, replace a voltage source with a short circuit and a current source with an open circuit. Keep all resistors in place. Solve each simpler circuit, then add the results with their signs.
Worked example: V1 = 20 V with R1 = 4 Ω, V2 = 10 V with R2 = 2 Ω, and R3 = 8 Ω from node A to ground. With V1 alone, R2 ∥ R3 = 1.6 Ω, so VA' = 20 × 1.6/5.6 = 5.714 V. With V2 alone, R1 ∥ R3 = 2.667 Ω, so VA'' = 10 × 2.667/4.667 = 5.714 V. The total is VA = 11.43 V and I3 = 1.429 A, the same as nodal analysis gives.
Exam tips and common mistakes
- Superposition works for voltages and currents only. Power is not linear: in the example, P3 = 16.33 W but P' + P'' = 8.16 W.
- Keep the direction of each partial current consistent before adding.
- Dependent sources are never turned off. They stay in every case.
- A resistor in series with a current source has no effect on the rest of the circuit.
The table shows every quantity for each case side by side, ready to copy into a solution.
Frequently asked questions
Which circuit does the tool solve?
Two sources feeding one node A: V1 with series R1, and either V2 with series R2 or a current source Is, with a load R3 from A to ground. This covers most textbook superposition problems.
Why can't I add the powers?
Power is I²R, which is not linear. (I' + I'')² is not I'² + I''², so add the currents first and then find the power.
How is a current source turned off?
Replace it with an open circuit (zero current). A voltage source is replaced with a short circuit (zero volts).
Is this tool free?
Yes. You fill in a short form once to see your result, and the other Uncodemy tools then open without it. All the maths runs in your browser.