A quantity of an ideal gas is compressed to half" its initial volume. The process may be adiabatic, isothermal or isobaric. Rank those three processes in order of the work required of an external agent, least to greatest.
doesn't adiabatic mean no work, so it would be the least, correct? and what about the other two?
You are correct that an adiabatic process does not involve any heat transfer, and therefore, no work is required from an external agent. So, an adiabatic process would indeed require the least work.
Now, let's discuss the other two processes:
1. Isothermal process: In an isothermal process, the temperature of the gas remains constant. To compress the gas, an external agent needs to constantly remove heat from the gas to maintain the temperature. This removal of heat requires work from the external agent. Therefore, an isothermal process would require more work than an adiabatic process but less work than an isobaric process.
2. Isobaric process: In an isobaric process, the pressure of the gas remains constant. To compress the gas, an external agent needs to exert a force over a certain distance. Since the pressure is constant, the work done is simply given by the product of the pressure and the change in volume. Therefore, an isobaric process would require more work than both an adiabatic and an isothermal process.
So, to rank the three processes in order of the work required from an external agent, it would be as follows:
1. Adiabatic process (least work)
2. Isothermal process
3. Isobaric process (greatest work)