Assertion : Zeroth law can also be termed as law of thermal equilibrium.
Reason : Two objects in thermal equilibrium with the third one, are in thermal equilibrium with each other.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Answer

B

Explanation

In an isothermal process change in internal energy `(Delta E)` is zero (as it is a function of temperature).
`therefore` According to first law of thermodynamics
`because q+w = Delta E`, hence `Q=-W` (if `Delta E = 0`)
If a system undergoes a change in which internal energy of the system remains constant (i.e., `DeltaE =0`), then -W=Q. This means that work done by the system equals the heat absorbed by the system.