Question

What are the limitations of the superposition theorem?

Answer 1

Hint: In order to solve this question we need to understand what superposition theorem is. So superposition theorem states that in any linear network containing only linear sources (Voltage-current) the overall branch current or voltage in the network is equal to algebraic sum of responses of individual source making all other sources inoperative or by replacing them with their internal impedance.

Complete step by step answer:
A voltage source can be made inoperative by short circuiting it and current source is made inoperative by open circuiting, here both replaced by their internal impedance.

Limitations of superposition theorem:
-Superposition theorem becomes invalid when the circuit contains electronic non-linear devices like diodes, transistors etc. Superposition in mathematics is only true when the vectors can be added linearly u on case on non-linear device voltage and current is not directly proportional rather they have different behavior at large or very small current.

-Superposition theorem cannot be applied for power calculations because power of any electronic device is not linear in current or voltage. Power expressions contains quadratic current or voltage such as $P = {I^2}R$ Or $P = \dfrac{{{V^2}}}{R}$.Here $I$ is current, $V$ is voltage and $R$ is resistance.

Note: It should be remembered that the superposition theorem is only valid when the circuit contains more than or equal to two linear devices. So for a single device it is insufficient to calculate from the superposition theorem. Current source is open circuited so that resistance becomes infinite and current could not flow while voltage source is short circuited so that resistance becomes zero and large current flows so a very less voltage drop.