Question

A 1500-W heater is connected to a 120-V line for 2.0 hours. How much heat energy is produced?

Answer 1

A joule is equal to one watt per second and so we must find out how many seconds are in two hours. A shortcut you can use is remove the zeros and multiplying the remaining numbers before adding the the zeros back to the total of your result 6 x 6 x 2 = 72 and thus 60 x 60 x 2 = 7200 72 x 15 = 1080 and thus 7200 x 1500 = 10800000 joules one mega joule equals one million joules So we can simplify things and say 10.8 MJ