# A charge of 25 C passes through a circuit every 4 s. If the circuit can generate 5 W of power, what is the circuit's resistance?

current$I = \frac{Q}{t} = \frac{25}{4} = 6.25 A$
Resistance $R = \frac{P}{I} ^ 2 = \frac{5}{6.25} ^ 2 = 0.128 \Omega$