Question

Temperature of the system decreases in an
(a) Adiabatic compression
(b) Isothermal compression
(c) Isothermal expansion
(d) Adiabatic expansion

Answer 1

Hint: In adiabatic processes, there is no flow of heat and mass in and out of the system. In the isothermal process, the temperature does not change, that is, it is kept constant.

Complete step by step solution: For solving this question, we will consider each option given in the question.
-Adiabatic compression process is the compression in which heat is not added or removed from a system and the internal energy of the system is increased and this is equal to the external work that is done on the system. So, there will be an increase in the temperature, but it does not escape the system. As this temperature increases, the pressure of the system will be more than the volume when adiabatic compression occurs.
-We know the isothermal process is the change in a system which occurs at a constant temperature. Here $$\mathrm{\Delta }T$$ is equal to zero. Isothermal compression is the compression occurring at a constant temperature. So, option (b) is incorrect, because in the question it is given that temperature decreases.
-Isothermal expansion is the expansion of a system at a constant temperature. In this also the temperature does not change. So option(c) is also incorrect.
-In adiabatic expansion is an ideal behaviour for a closed system. Here, there will be no flow of heat, but when the pressure is kept constant, the temperature decreases.

Thus, only in adiabatic processes, there is change in temperature. In adiabatic compression, temperature increases. In adiabatic expansion, temperature decreases. So, the correct option is (a).

Note: In compression, the volume of the system is decreased, so the pressure and temperature will increase, if there is no heat flow. In expansion, the volume decreases, so pressure and temperature decrease.