A bulb is rated 5 V and 500 mA. Calculate its (a) power, (b) resistance, and (c) energy consumed when it is lighted for 4 hours.
(a) Power = P = VI
=5×0.5=2.5W
(b) Resistance (R) =VI=50.5=10 Ω
(c) Energy consumed =VIt=P×t
E=2.5×4×3600J
E=36000J
E=36 kJ