# max power transfer theorem

Joined Jan 19, 2004
220
the other day we were conductiin expt for verification of max power transfer theorem.
we ogt the results more or less accurately but i hav a few doubts...
max power is said 2 be transfered from source to load if Ri=RL
at this condition efiiciency is 50%
on increasing Rl greater than Ri...we found that efficiency increases :blink: :blink:
theoriticall it becomes 100% for Ri=0...which is practically impossible..
my question is how can efiiciency be greater then 50%...if max power is transfered at 50% efficiency :blink:

#### pebe

Joined Oct 11, 2004
626
Originally posted by haditya@Nov 19 2004, 02:41 PM
the other day we were conductiin expt for verification of max power transfer theorem.
we ogt the results more or less accurately but i hav a few doubts...
max power is said 2 be transfered from source to load if Ri=RL
at this condition efiiciency is 50%
on increasing Rl greater than Ri...we found that efficiency increases :blink: :blink:
theoriticall it becomes 100% for Ri=0...which is practically impossible..
my question is how can efiiciency be greater then 50%...if max power is transfered at 50% efficiency :blink:
[post=3662]Quoted post[/post]​
It's more accurate to say that maximum energy is transferred when the *output* resistance Ro=RL, because the power source has an output resistance, and the load has an input resistance.

When Ro=0, it's the same as wiring a lamp direct to the mains supply, and all available power can be taken by the lamp.

But the max power Ro=RL concept is applicable when you are faced with a power source that has a finite Ro, and it is necessary to match the load so that it can take maximum power.