Final answer:
The change in internal energy of a system when 30J of heat is added and 20J of work is done by it is an increase of 10J. This is calculated using the first law of thermodynamics.
Step-by-step explanation:
If a system has 30J of heat added to it, and it does 20J of work, the change in its internal energy can be determined using the first law of thermodynamics. This law is usually expressed as ΔU = Q - W, where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system. In this case:
- Q (heat added to the system) = 30J
- W (work done by the system) = 20J
Plugging these values into the equation gives:
ΔU = 30J - 20J
The change in internal energy (ΔU) is:
ΔU = 10 J
Therefore, the internal energy of the system increases by 10J after 30J of heat is added and 20J of work is performed by the system.