Question

a gas is compressed from the volume of 2m3 to the volume of 1m3 at the constant pressure of 100 N/m2 . then it is heated at constant volume by supplying 150J of energy .As the result the internal energy of the gas is

Answer 1

The internal energy of the gas is 50 J.

1) We know, by the first law of thermodynamics, Q = U + W

Where, Q is the heat supplied, U is the internal energy, W is the work done.

2) In physics, the general notation is that, Q is positive when heat is supplied to the system and vise versa.

3) Again, work is taken positive when work is being done by the system.

4) So, work done in a constant pressure process is, W = P ( V1 - V2 )

5) Given, V1 = 2 m^3, V2 = 1m^3, P = 100 N/m^2.

6) So, W = 100 J. And Q supplied = 150 J

7) By definition, U = Q - W = 150 - 100 = 50J.