Question

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?

Answer 1

The resistance is `11.52` `Omega`

Explanation:

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`