Heat engine takes energy from a hot reservoir(having high temperature) and uses part of it to do work,& exhaust a part of the energy to a cold reservoir(having low temperature). S...
Option A and B are correct answer .A machine operating between two temperatures can only be an engine if it's efficiency is less than the carnot engine working between the same two...
Remember, for reversible heat engine, we have two fromulas for calculating efficiency, one in terms of heat exchange and other in terms of temperatures of sink and source. if effic...