## College Physics (4th Edition)

(a) $E = 262~J$ (b) $P = 8.1\times 10^{-3}~W$
(a) We can find the total charge: $Q = I \times t$ $Q = (18.0\times 10^{-3}~A)(9.0~h)(\frac{3600~s}{1.0~h})$ $Q = 583.2~C$ We can find the energy supplied by the solar cell: $E = V~Q$ $E = (0.45~V)(583.2~C)$ $E = 262~J$ (b) We can find the power: $P = \frac{Energy}{time} = \frac{262~J}{(9.0~h)(3600~s/h)} = 8.1\times 10^{-3}~W$