The Superposition theorem is a powerful tool used in circuit analysis to determine the response (voltage or current) in a linear circuit that has multiple independent sources. The principle of the theorem is that the total response in any part of a linear circuit containing multiple independent sources is equal to the sum of the responses caused by each independent source acting alone, while all other independent sources are turned off.

When we 'turn off' an independent voltage source, we replace it with a short circuit (zero voltage). When we 'turn off' an independent current source, we replace it with an open circuit (zero current). Dependent sources are left as they are.

Applying Superposition Theorem for Circuit Analysis

Here’s how the Superposition theorem is typically applied:

1. Select one independent source in the circuit.
2. Turn off all other independent sources (voltage sources become short circuits, current sources become open circuits). Dependent sources remain active.
3. Calculate the voltage or current in the specific element of interest due to this single active source.
4. Repeat steps 1-3 for each independent source in the circuit.
5. Algebraically sum the individual voltages or currents calculated in step 3 to find the total voltage or current in the element when all sources are active.

Superposition Theorem and Its Applicability

The Superposition theorem is based on the property of linearity. A linear circuit is one where the relationship between voltage and current is linear (e.g., Ohm's Law, $\text{V} = \text{IR}$). Circuit elements like resistors, capacitors, and inductors are linear when their values are constant, and ideal voltage/current sources are linear.

The theorem is directly applicable for finding:

• Voltage across any element in the circuit.
• Current through any element in the circuit.

However, the Superposition theorem is not applicable for determining power. Power is calculated using formulas like $\text{P} = \text{VI}$, $\text{P} = \text{I}^2\text{R}$, or $\text{P} = \text{V}^2/\text{R}$. These relationships involve the square of voltage or current, or the product of voltage and current, making power a non-linear quantity. If you were to sum the power contributed by each source individually, it would not give the correct total power when all sources are active. Therefore, to find the total power in an element using Superposition, you must first find the total voltage and current using the theorem and then calculate power using these total values.

Based on the principle of linearity and how the theorem is applied, the Superposition theorem is only applicable for determining voltage and current.

Let's look at the options provided:

• Power: Incorrect, as power is a non-linear quantity and cannot be directly superposed.
• Voltage: Partially correct, but the theorem is also applicable for current.
• Voltage and current: Correct, as the theorem is used to find both of these linear quantities.
• Current: Partially correct, but the theorem is also applicable for voltage.

Thus, the Superposition theorem is applicable for determining both voltage and current in a linear circuit.

Revision Table: Key Aspects of Superposition Theorem

Additional Information on Circuit Theorems

Understanding the Superposition theorem is crucial for analyzing circuits, especially those with multiple sources. It's one of several circuit theorems that simplify the analysis of complex networks. Other important theorems include:

• Thevenin's Theorem: Simplifies a linear circuit into a single voltage source in series with a single resistor.
• Norton's Theorem: Simplifies a linear circuit into a single current source in parallel with a single resistor.
• Maximum Power Transfer Theorem: Used to find the load resistance that receives maximum power from a source.

Each theorem has its specific applications and can simplify circuit analysis depending on the goal. Superposition is particularly useful when you need to see the contribution of each source to the overall response in a circuit element.