The internal energy of an ideal gas increases during an isothermal process when the gas is

Two identical containers $A$ and $B$ with frictionless pistons contain the same ideal gas at the same temperature and the same volume $V$. The mass of the gas in $A$ is ${m_A}$ and that in $B$ is ${m_B}$. The gas in each cylinder is now allowed to expand isothermally to the same final volume $2V$. The changes in the pressure in $A$ and $B$ are found to be $\Delta P$ and $1.5 \Delta P$ respectively. Then:

In an isothermal process,which statement is wrong?

Can the change in internal energy of an ideal gas be non-zero during an isothermal process?

Two identical containers $A$ and $B$ with frictionless pistons contain the same ideal gas at the same temperature and same volume $V$. The mass of the gas in $A$ is $m_{A}$ and that in $B$ is $m_{B}$. The gas in each cylinder is now allowed to expand isothermally to the same final volume $2V$. The changes in the pressures of the gases in $A$ and $B$ are found to be $2\Delta P$ and $3\Delta P$ respectively. Then the relation between $m_{A}$ and $m_{B}$ is

During which thermodynamic process does $T$ remain constant, while the other two variables $P$ and $V$ change?