This theorem is applicable for linear and bilateral networks. Let us see the statement of the theorem.

**In an any multisource complex network contains linear bilateral elements, the voltage across or current pass through any given element of the network is identical to the algebraic sum of the individual voltages or currents, produced separately across or in that element by each source acting separately, when all the residual sources are replaced by their relevant internal resistances.**

__Statement :__
This theorem is also called as Superposition principle. In other terms, it can be stated as; the response in any element of linear, bilateral network consisting more than one source is the sum of the responses produced by the sources, each acting independently. The response means the voltage across the element or the current in the element. The superposition theorem does not apply to the power as power is proportional to square of the current, which is not a linear function.

###
**Explanation of Superposition Theorem**

Consider a network, shown in the Fig-a, having two voltage sources V

_{1}and V_{2}.
Let us calculate, the current in branch A-B of the network, using superposition theorem

Step 1) According to Superposition theorem, consider each source individually. Let source V

_{1}volts is acting independently. At this time, other sources should be replaced by internal impedances.
But as internal impedance of V

_{2}is not given, the source V_{2}should be replaced by short circuit. Thus circuit becomes, as shown in the Fig-b.
Using any of the network reduction techniques discussed earlier, obtain the current through branch A-B i.e. IAB due to source V

_{1}alone.
Step 2) Now consider source V

_{2}volts alone, with V_{1}replaced by a short circuit, to obtain the current through branch A-B. The equivalent circuit is shown in the Fig-c.
Obtain I

_{AB}due to V_{2}alone, by using any of the network reduction techniques discussed
Step 3) According to the Superposition theorem, the sum current through the branch A-B is sum of the currents through branch A-B produced by every source acting separately.

####
**Steps to Apply Superposition Theorem**

Step 1: Decide on a single source acting alone. Short the other voltage sources and open the current sources, if internal resistances are not known. If known, replace them by their internal resistances.

Step 2: Find the current through or the voltage across the required element, due to the source under consideration, using a suitable network simplification technique.

Step 3: Repeat the above two steps for all the sources

Step 4: Add the individual effects produced by individual sources, to obtain the total current in or voltage across the element.