Question

Assertion : Heat energy is completely transformed into work during the isothermal expansion of a gas. 

Reason : During an isothermal process, the change in internal energy of a gas due to decrease in pressure is nullified by the change due to increase in volume.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option  (a) Both A and R are true and R is the correct explanation of A

Explanation:

In an isothennai expansion, temperature is maintained constant so intemal energy change is zero. (ΔE=0).

 According to the first law of thermodymamics,

ΔE= q + w

q = heat, w work done ⇒ q = -w

This shows that work is done by the system at the expense of heat absorbed.