Correct Answer - Option 3 : dU = -dW
Concept:
The first law of thermodynamics
- It states that energy can neither be created nor destroyed, but can only be converted from one form to another.
- The heat energy supplied to a thermodynamic system increases its internal energy and the remaining heat energy is converted into the work done by the system.
- If dQ is the heat given to the thermodynamic system and dU is its change in internal energy and dW is the work done by the system, then first of law of thermodynamics gives
dQ = dW + dU
Adiabatic process:
- When a thermodynamic system undergoes a change in such a way that no exchange of heat takes place between Systems and surroundings, the process is known as an adiabatic process.
- Change in heat or dQ is zero for adiabatic process.
Calculation:
Given by first Law
dQ = dW + dU -- (1)
Given in adiabatic process
dQ = 0 -- (2)
Combining first and second
0 = dW + dU
So,
dU = - dW
That means the work done is negative of change in internal energy in the adiabatic process.
