In a heat engine, if 500 j of heat enters the system, and the piston does 300 j of work, what is the final internal (thermal) energy of the system if the initial energy is 1,500 j?

800 j

1,300 j

200 j

1,700 j

The final energy is 1,700 J

Explanation: According to first law of thermodynamics:

=Final energy-initial energy=Change in internal energy

q = heat absorbed or released

w = work done by or on the system

w = work done by the system=  {Work done by the system is negative as the final volume is greater than initial volume}

q = +500J   {Heat absorbed by the system is positive}

w = work done by the system = -300J