# A charge of 18 C passes through a circuit every 12 s. If the circuit can generate 4 W of power, what is the circuit's resistance?

Mar 5, 2017

Calculate the current by dividing charge by time:

$I = \frac{Q}{t} = \frac{18 C}{12 s} = 1.5 A$

Electric power is given by

$P = I V = I \left(I R\right) = {I}^{2} R$

Therefore,

$R = \frac{P}{I} ^ 2 = \frac{4 W}{1.5 A} ^ 2 = 1.78 \Omega$