Question

The current in a 120-V reading lamp is 2.4 A. If the cost of electrical energy is $0.090 per kilowatt-hour, how much does it cost to operate the light for an hour? (Do not round to the nearest cent.)

Answer 1

you can use Joule's law to get the answer

Answer 2

Using Ohm's Law:\[P=IV=(2.4A)(120V)=288W=0.288kW\]\[0.288kW*1hr=0.288kWh\]\[0.288kWh*\frac{$0.090}{kWh}=0.02592\space cents\]So it costs about 3 cents.