## Superposition Theorem MCQ (Interview-Exam) Question-Answer

**Q.1** In superposition theorem, when we consider the effect of one current source, all the other voltage sources are ____________.

**A.** Opened

**B.** Undisturbed

**C.** Shorted

**D.** Removed

**Ans : **Shorted

**Q.2** In superposition theorem, when we consider the effect of one voltage source, all the other voltage sources are ____________.

**A.** Opened

**B.** Undisturbed

**C.** Shorted

**D.** Removed

**Ans : **Shorted

**Q.3** In superposition theorem, when we consider the effect of one current source, all the other current sources are ____________.

**A.** Opened

**B.** Undisturbed

**C.** Shorted

**D.** Removed

**Ans : **Opened

**Q.4** In superposition theorem, when we consider the effect of one voltage source, all the other current sources are ____________.

**A.** Opened

**B.** Undisturbed

**C.** Shorted

**D.** Removed

**Ans : **Opened

**Q.5** Find Vx due to the 3A source.

**A.** 78V

**B.** 48V

**C.** 56V

**D.** 38V

**Ans : **48V

**Explanation: ** I20 = 3*80/(20+80)=2.4A

Vx=20*2.4=48V.

**Q.6** Find the value of Vx due to the 16V source.

**A.** 3.2V

**B.** 6.3V

**C.** 4.2V

**D.** 2.3V

**Ans : **3.2V

**Explanation: ** Vx = 16*20/(20+80)=3.2A.

**Q.7** Find the voltage due to the 15A source.

**A.** 2V

**B.** 6V

**C.** 0V

**D.** 4V

**Ans : **00VV

**Explanation: ** Due to the 15A current source, the 10V and 16V sources become smaller and the 3A source acts as an open circuit. Since the 10V source is small, it acts as a low resistance path and current only flows within that loop and does not flow into the 20 ohm resistor. Therefore the voltage is 0V.

**Q.8** Find the value of Vx due to the 10V source.

**A.** 2V

**B.** 4V

**C.** 1V

**D.** 3V

**Ans : **2V

**Explanation: ** Vx=10*20/(80+20)=2V.

**Q.9** Superposition theorem does not work for ________.

**A.** Voltage

**B.** Works for all: current, voltage and power

**C.** Current

**D.** Power

**Ans : **Power

**Q.10** Superposition theorem is valid for _________.

**A.** Non-linear systems

**B.** Neither linear nor non-linear systems

**C.** Linear systems

**D.** Both linear and non-linear systems

**Ans : **linear systems

## Superposition Theorem

**1. Principle:** The Superposition Theorem states that in a linear circuit containing multiple independent sources, the voltage across (or current through) any element in the circuit can be found by considering the effect of each source separately, while treating all other sources as inactive or replaced by their internal impedance.

**2. Linearity Requirement:** The theorem only applies to linear circuits, where the relationship between voltage and current follows Ohm’s law. This means that the behavior of the circuit elements must be independent of the magnitude of the applied voltage or current.

**3. Independent Sources:** The theorem applies to circuits containing multiple independent sources, such as voltage sources and current sources. These sources can be DC (direct current) or AC (alternating current).

**4. Superposition Principle:** The essence of the theorem lies in the superposition principle, which states that in a linear system, the net response at a given point caused by multiple inputs is the sum of the responses that would be caused by each input individually.

**5. Procedure:** To apply the Superposition Theorem, each independent source is considered one at a time while the others are temporarily removed or replaced. The resulting voltage or current due to each source is then calculated. Finally, these individual results are summed to obtain the total voltage or current.

**6. Applicability:** The Superposition Theorem is particularly useful for simplifying the analysis of complex circuits with multiple sources. It can simplify calculations by breaking down the problem into smaller, more manageable parts.

**7. Limitations:** The Superposition Theorem cannot be applied to circuits containing dependent sources (sources whose output depends on some other voltage or current in the circuit), non-linear elements (such as diodes and transistors), or time-varying elements (such as capacitors and inductors).

**8. Verification:** After calculating the individual contributions of each source, it’s essential to ensure that the final result satisfies Kirchhoff’s laws and any other relevant circuit principles. This step helps verify the correctness of the analysis.