Question

A heat engine undergoes a process at which its internal energy increases 275 J while doing 360 J of work. How much heat is taken in (or given out) by the engine during this process?

Answer 1

When the engine does work its internal energy should decrease but since the internal energy is increasing in this case this means that the external energy that is the heat taken during this process is the sum of the work done by the engine and the increase in internal energy.

heat engine is doing work of 360 J.

Internal energy in increasing by 275 J.

Therefore the heat taken in during the process = 360+275= 635 J

The internal energy of the system will decrease when the system does work and/or gives off heat. Since the heat given out is 150 J and the reduction in internal energy is 400 J, the work done by the engine is 400 -150 = 250 J.

When the internal energy is reduced, the system is cooled.