# power versus resistance

#### buseh

Joined Feb 9, 2007
1
i need some help with graph of power versus load of resistance when there is a source of emf with internal resistance. maximum and min power?? how to do this??

#### Papabravo

Joined Feb 24, 2006
18,839
i need some help with graph of power versus load of resistance when there is a source of emf with internal resistance. maximum and min power?? how to do this??
Twinkle twinkle little star
Power's equal I squared R

#### Dave

Joined Nov 17, 2003
6,969
Further to Papabravo's answer, you need to compute the power values for each value of resistance you have. For this you need to assume constant current and voltage to get the plot for Power Vs Resistance.

So for P = (I^2)*R

I = some constant value

And you can calculate P for different values of R. Plot resistance on the x-axis and power on the y-axis.

Dave

#### recca02

Joined Apr 2, 2007
1,212
when there is a emf source with internal source try making a eq circuit and
place internal resistance in series with emf source use thevenin's theorem
to get simplified circuit in case of complex circuits, it really isnt that hard,
one important clue for max power the load impedance must equal the circuit's
thevenin's eq ckt impedance.