Question

In a heat engine, 700 J of heat enters the system, and the piston does 400 J of work.

What is the final internal (thermal) energy of the system if the initial energy is 1200 J?

Responses

300 J

300 J

900 J

900 J

1100 J

1100 J,

1500 J

Answer 1

2300J

Step-by-step explanation:

The first law of thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system:

ΔU = Q - W

Where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.

In this case, ΔU is what we want to find, Q is 700 J, and W is -400 J (note that the work done by the system is negative because it is done on the surroundings). Substituting these values into the equation:

ΔU = Q - W

ΔU = 700 J - (-400 J)

ΔU = 700 J + 400 J

ΔU = 1100 J

The final internal energy of the system is therefore 1100 J + the initial energy of 1200 J, which equals 2300 J.