Question

The current in a 120-V reading lamp is 2.6 A. If the cost of electrical energy is $0.075 per kilowatt-hour, how much does it cost to operate the light for an hour

Answer 1

Answer:

P(power) = I V = 2.6 * 120 = 312 J/s

P = 312 J/s / 1000 J/kw ]= .312 kw/sec

E = P * t = .312 kw    energy used in 1 sec by bulb

To use .312 kw for an hour costs $.075

So .312 * .075 = .0234 $ = 2.34 cents      each hour