Question

you replace a 40 w incandescent lightbulb with an 8 w led bulb. if you leave your lights on for 24 hours a day how much energy are you saving each day by replacing the bulb

Answer 1

power is the measure of how much energy is being used by the bulb per unit of time. in this case, power is given in watts, where 1 W = 1 joule/second

the difference in power between the two bulbs is simply 40 - 8 = 32 W. however, the question asks for the energy difference (not the power difference).

since 32 W = 32 joules/second,simply multiply this by the # of seconds in 24 hours to get the energy, in joules, saved per day. as a reminder, 24 hours = 86400 seconds

that'll give you energy in joules. if the problem specifies that it wants a different unit, please let me know.