Question

An adiabatic process occurs at constant
(A) Temperature
(B) Pressure
(C) Heat
(D) Temperature and pressure

Answer 1

Hint :We know that a system can change its initial state to its final state via many paths and this manner of changing state of a system is known as a thermodynamic process. The process may occur under a variety of conditions which should be defined because many things depend upon the nature of the process. The various thermodynamic processes are isothermal process, adiabatic process, isochoric process and isobaric process.

Complete Step By Step Answer:
In thermodynamics, an adiabatic process is defined as a process in which no transfer of heat takes place from the system to the surrounding neither in case of expansion nor during compression. It can be either a reversible or an irreversible process. The essential conditions for a process to be adiabatic are as follows:
1. The process must be perfectly insulated.
2. The process must be carried out so quickly in order to avoid any transfer of heat from the system to its surroundings.
According to the first law of thermodynamics, the energy can be converted from one form to another form with the interaction of heat, work and internal energy but under any circumstance, the energy cannot be created nor be destroyed. Mathematically it is represented as follows:
 $ dU = q + w $
For an adiabatic process, $ q = 0 $ therefore the change in internal energy will be equal to the work done by the system. This indicates that the work must be done at the expense of internal energy, since no heat is being supplied from the surroundings.
Thus, we can conclude that in an adiabatic process, the quantity which remains constant is the total heat of the system.
Hence, the correct option is (C).

Note :
Remember that no heat transfer does not mean that the temperature of the system is constant, but rather that no heat is transferred to or from the system. In an adiabatic system, if a work is performed, then $ dU $ has to change the value which is negative the amount of work performed and as internal energy changes, so the temperature has to change.