What is Thevenin Theorem

Thevenin’s Theorem states:

Any linear electrical network containing voltage sources and resistances can be replaced, as seen from two terminals, by an equivalent circuit consisting of a single voltage source VthV_{th}Vth? in series with a resistance RthR_{th}Rth?.

How to find Thevenin equivalent

1. Remove the load connected across the terminals.

2. Find VthV_{th}Vth?: the open-circuit voltage across the terminals.

3. Find RthR_{th}Rth?: deactivate all independent sources

   • Voltage sources → short circuit

   • Current sources → open circuit
     (or use Rth=Vth/IscR_{th} = V_{th}/I_{sc}Rth?=Vth?/Isc?)

4. Replace the original network with VthV_{th}Vth? in series with RthR_{th}Rth?.

Why it’s useful

• Simplifies complex circuits

• Makes load current and power calculations easy

• Very helpful in circuit analysis and design