Question

A system $X$ is neither in thermal equilibrium with $Y$ nor with $Z$. Then what can we say about the systems $Y$ and $Z$?

• A. $\text{They must be in thermal equilibrium.}$
• B. $\text{They cannot be in thermal equilibrium.}$
• C. $\text{May be they are in thermal equilibrium.}$
• D. $\text{none of these}$

Answer 1

The correct option is C

$\text{May be they are in thermal equilibrium.}$

$\text{Let the temperatures of X, Y and Z be}{T}_x,T_{y}and{T}_z,\text{respectively}$

$\text{Now,}$

$T_x\ne T_y$

$\text{and}$

$T_x\ne T_z$

$\text{This does not tell us anything about}{T}_{y}and{T}_z,\text{except that they are not equal to}{T}_x$

$\text{So,}{T}_y=T_z,and{T}_y\ne T_z,\text{both are possibilities!}$

$\text{Hence, option (c) is correct.}$