Question

A machine is 12% efficient. If useful work done by the machine is 6 joules then calculate the total amount of heat

Answer 1

$E = A+Q;\\ A=6~\text{J};\\ k = \frac{A}{E} = 0.12;\\ Q = E-A = \frac{A}{k}-A = \frac{1-k}{k}A = 44~\text{J}.$