Question

If  ΔU and  ΔW represent the increase in internal energy and work done by the system respectively in a thermodynamical process, which of the following is true?

(a) Δu = -ΔW, in an adiabatic Process

(b) Δu = ΔW, in an isothermal Process

(c) Δu = ΔW, in an adiabatic Process

(d) Δu = -ΔW, in an isothermal process

Answer 1

Correct option (a) Δu = -ΔW, in an adiabatic Process

Explanation:

According to first law of thermodynamics

ΔQ = Δu + ΔW, 

where,

ΔQ = Heat supplied to the system

 Δu = Increase in internal energy of the system

ΔW = Work done by the system

For an adiabatic process

ΔQ = 0

:. Δu =  - ΔW, 

For an isothermal process

Δu = 0

:. ΔQ  =  ΔW, 

Hence, option (a) is true.