A charge of #15 C# passes through a circuit every #12 s#. If the circuit can generate #18 W# of power, what is the circuit's resistance?

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Answer 1 · 2016-03-03T12:35:55

The resistance is #11.52# #Omega#

First, let's think about what we are trying to calculate. We know the power generated from the circuit which is given by Joule's law:

#P=I*V = 18# #W#

We have also been given the rate of charge flow, which is a current:

#I = Q/t = (15C)/(12s) = 1.25# #A#

We can substitute this current into the first equation and solve for the voltage:

#V = (18W)/(1.25A) = 14.4# #V#

Now we have a current and a voltage and want to find a resistance. We know Ohm's Law relates all three of these:

#V=I*R#

Rearranging to find the resistance:

#R = V/I = (14.4V)/(1.25A) = 11.52# #Omega#