Science electricity efficiency question?

Science & Mathematics by Anonymous 2018-05-11 11:09:36

Social Science

2 answers

A flashlight produces 80 joules of light and uses 400 watts every 5 seconds, what's the rate of efficiency and how do you get it?

Anonymous

The question is misleading. It should say A flashlight produces 80 joules of light every 5 seconds and uses 400 watts 80 Joules per 5 seconds is 16 joules per second, ie 16 Watts so 16/400 = 4/100 = 4%
Anonymous

ɳ = 100*(80/(400*5)) = 8000/2000 = 4.0 % , which is typical of a bulb lamp