Question

A closed system receives heat at a rate of 2 kW from a source at 1000 K, electrical power at a rate of 2 kW and shaft power at a rate of 2 kW. Determine the net rate of

(a) Energy transfer and

Answer 1

The net change in internal energy for the system is 9.00 J, calculated by accounting for initial and later heat transfers and work done by and on the system according to the first law of thermodynamics.

Step-by-step explanation:

When considering a system with heat transfer and work, we apply the first law of thermodynamics which states that the change in internal energy (ΔU) of the system is equal to the heat (Q) added to the system minus the work (W) done by the system. In the given scenario, heat transfer occurs twice and work is done twice on or by the system.

Initially, there is a heat transfer of 40.00 J to the system and the system does 10.00 J of work. This results in an increase in internal energy (ΔU1) of 40.00 J - 10.00 J = 30.00 J. Later, there is a heat transfer of 25.00 J out of the system and 4.00 J of work is done on the system. This results in a decrease in internal energy (ΔU2) of -25.00 J + 4.00 J = -21.00 J.

Overall, the net change in internal energy (ΔU) is the sum of ΔU1 and ΔU2, which is 30.00 J - 21.00 J = 9.00 J. Thus, the system's internal energy increases by 9.00 J.