In an isothermal expansion of an ideal gas, there cannot be any change in the internal energy otherwise the temperature would change. So hence we know that all the heat goes into work. Knowing that $PV=nRT$ as the equation of state and $T$ being constant in this process, we see that $P$ is inversely proportional to $V$.

Does that mean in order to feasibly realize an isothermal expansion we would need to do the following:

1. Put the ideal gas in a cylinder with a piston and some amount of weight on it to reach some pressure.
2. Find a heat reservoir equal to the temperature of the gas.
3. Slowly lift weight off of the piston according to $P \propto 1/V$.

The last part is kind of the strange part. We have to lift some weight off otherwise the volume won't change. But why can't we quickly lift the weight off? So the external pressure changes from some large number to a very smaller number? Would that be approximately an adiabatic expansion?

In an isothermal expansion of an ideal gas, there cannot be any change in the internal energy otherwise the temperature would change. So hence we know that all the heat goes into work. Knowing that $PV=nRT$ as the equation of state and $T$ being constant in this process, we see that $P$ is inversely proportional to $V$.

Does that mean in order to feasibly realize an isothermal expansion we would need to do the following:

1. Put the ideal gas in a cylinder with a piston and some amount of weight on it to reach some pressure.
2. Find a heat reservoir equal to the temperature of the gas.
3. Slowly lift weight off of the piston according to $P \propto 1/V$.

The last part is kind of the strange part. We have to lift some weight off otherwise the volume won't change. But why can't we quickly lift the weight off? So the external pressure changes from some large number to a very smaller number? Would that be approximately an adiabatic expansion?

Editted: Just want to confirm the necessity of the last part where we are slowly decreasing the force applied by the piston. Not sure how to do that practically, you would need some kind of electronically controlled device to slowly "lift the weights off".

In an isothermal expansion of an ideal gas, there cannot be change in internal energy otherwise the temperature would change. So hence we know that all the heat go into work. Knowing that PV=nRT and T being constant, we see that P is inversely proportional to V.

Does that mean in order to feasibly realize an isothermal expansion we would need to do the following:

1. Put the ideal gas in a cylinder with a piston and some amount of weight on it to reach some pressure.
2. Find a heat reservoir equal to temperature of the gas.
3. Slowly lift weight off of the piston according to $P \propto 1/V$.

The last part is kind of the strange part. We have to lift some weight off otherwise the volume won't change. But why can't we quickly lift the weight off? So the external pressure changes from some large number to a very smaller number? Would that be approximately an adiabatic expansion?

In an isothermal expansion of an ideal gas, there cannot be any change in the internal energy otherwise the temperature would change. So hence we know that all the heat goes into work. Knowing that $PV=nRT$ as the equation of state and $T$ being constant in this process, we see that $P$ is inversely proportional to $V$.

Does that mean in order to feasibly realize an isothermal expansion we would need to do the following:

1. Put the ideal gas in a cylinder with a piston and some amount of weight on it to reach some pressure.
2. Find a heat reservoir equal to the temperature of the gas.
3. Slowly lift weight off of the piston according to $P \propto 1/V$.

The last part is kind of the strange part. We have to lift some weight off otherwise the volume won't change. But why can't we quickly lift the weight off? So the external pressure changes from some large number to a very smaller number? Would that be approximately an adiabatic expansion?