Network Theorems are useful in determining the unknown values of current, Resistance, Voltage etc in Electric Networks.
Thevenin’s theorem states that any two output terminals ( A & B ) of an active linear network containing independent sources (it includes voltage and current sources) can be replaced by a simple voltage source of magnitude Vth in series with a single resistor Rth where Rth is the equivalent resistance of the network when looking from the output terminals A & B with all sources (voltage and current) removed and replaced by their internal resistances and the magnitude of Vth is equal to the open circuit voltage across the A & B terminals.
