# A charge of 6 C passes through a circuit every 3 s. If the circuit can generate 24 W of power, what is the circuit's resistance?

Current is given by $I = \frac{Q}{t}$, so in this case is $I = \frac{6}{3} = 2$ $A$.
Power in an electric circuit is given by $P = {I}^{2} R$, which we can rearranged to make $R$ the subject: $R = \frac{P}{I} ^ 2 = \frac{24}{2} ^ 2 = 6$ $\Omega$.
Very briefly as an additional explanation, we often just remember Ohm's Law, $V = I R$, and $P = V I$ for power, and substitute to find the expression we need. In this case, substituting in $I R$ for $V$ in the law for power gives us $P = I R \times I = {I}^{2} R$.