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?
The resistance is
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:
We have also been given the rate of charge flow, which is a current:
We can substitute this current into the first equation and solve for the voltage:
Now we have a current and a voltage and want to find a resistance. We know Ohm's Law relates all three of these:
Rearranging to find the resistance: