1. MAXIMUM POWER TRANSFER THEOREM
In many electrical and electronic applications, we are interested in the amount of power received by a particular load (speaker, electric motor, antenna)
Electric systems are a source of power and a load connected to that source
Sources – Amplifiers, generators, power supplies
All linearly constructed sources can be reduced to their Thevenin equivalent
In DC circuits, the load can be represented by a resistance RL
Maximum Power Transfer Theorem

2. POWER DELIVERED TO LOAD
The source develops a voltage VL across the load and enables current IL to flow into it
The power delivered to the load resistance (RL) depends on the value of RL
Maximum Power Transfer Theorem

3. MAXIMUM POWER, CURRENT AND VOLTAGE CONDITIONS
Maximum current IL occurs when RL = 0 (shorted terminals)
The maximum voltage VL occurs when RL =  (open circuited terminals)
Yet load power PL = 0 for both cases
PL is maximum when RL equals the Thevenin equivalent resistance of the source, I.e. when RL = RTH
The maximum power transfer theorem is thus:
Maximum power is developed in a load when the load resistance equals the Thevenin resistance of the source to which it is connected
Maximum power is delivered when VL = ETH/2
Thus
Maximum Power Transfer Theorem