The first law of thermodynamics states that the energy can neither be created nor destroyed, but can be converted from one form to another. This takes place with the interaction of heat, work, and internal energy.
The mathematical representation of the first law of thermodynamics is:
|
ΔU = Q + W |
Where,
- ΔU is the total change in the internal energy of the system
- Q is the heat exchanged between the system and its surroundings
- W is the work done either by the system or on the system
Below is the table explaining the sign conventions for heat, internal energy, and work done:
|
ΔU |
Q |
W |
|
It will be positive if the temperature increases |
It will be positive if heat enters the gas |
It will be positive if the gas is compressed |
|
It will be negative if the temperature decreases |
It will be negative if heat leaves the gas |
It will be negative if the gas expands |
|
It will be zero if the temperature is constant |
It will be zero if no heat is exchanged |
It will be zero if the volume is constant |
