Question

The work performed by a heat engine

		1. equals the heat energy exhausted from the engine.
		2. equals the heat energy entering the engine.
		3. equals the change in the internal energy of the engine.
		4. equals the net heat flow into the engine.

Answer 1

From Second law of thermodynamics, which states that : ' no heat engine is 100% efficient , i.e. when heat is supplied to a heat engine , all the heat is not used to do work but some of the heat is transferred to a colder body .'

So, heat supplied to heat engine = work done by heat engine + heat given to colder body .

Therefore , Work done = heat supplied to heat engine - heat given to colder body

Which means that , work done = Net heat given to heat engine .

So option 4 is correct , equals the net heat flow in the heat engine.