The condition $dQ = dW$ holds good in which of the following?

During the isothermal expansion,a confined ideal gas does $(-150) \ J$ of work against its surroundings. This means that

$A$ piston of mass $M$ is hung from a massless spring whose restoring force law is given by $F = -kx^3$,where $k$ is the spring constant of appropriate dimension. The piston separates the vertical chamber into two parts,where the bottom part is filled with $n$ moles of an ideal gas. An external work is done on the gas isothermally (at a constant temperature $T$) with the help of a heating filament (with negligible volume) mounted in the lower part of the chamber,so that the piston moves up from a height $L_0$ to $L_1$. Calculate the total energy delivered by the filament. (Assume the spring to be in its natural length before heating.)

An ideal gas expands isothermally along $ab$ and does $600\,J$ of work. During the process,

In an isothermal change, an ideal gas obeys:

An isothermal process has a non-linear graph between: