# power versus resistance

Discussion in 'Physics' started by buseh, Feb 9, 2007.

1. ### buseh Thread Starter New Member

Feb 9, 2007
1
0
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??

2. ### Papabravo Expert

Feb 24, 2006
10,137
1,786
Twinkle twinkle little star
Power's equal I squared R

3. ### Dave Retired Moderator

Nov 17, 2003
6,960
144
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

4. ### recca02 Senior Member

Apr 2, 2007
1,211
0
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.