thermodynamics - What is the difference between $Q=Delta U+W$ and $Delta U=Q+W$?

Is $Q=\Delta U+W$ for when the the work is done from the system while $\Delta U=Q+W$ is for when the work is done by the system? Will anybody explain this to me, please?

When do we use $Q=\Delta U+W$ and when do we use $\Delta U=Q+W$?

Answer

It is a matter of convention. The sign convention of Clausius and the sign convention of IUPAC are the two prevailing sign conventions. Both of these assign a sign to the work done differently. The former, used primarily in physics assign a positive sign to the work done by the system while the latter assigns positive sign to the work done on the system. Hence, according to the convention youe are following, the form of the First law of thermodynamics will change:-
$$Q=\Delta U+W \quad \text{(Clausius convention)}$$ $$\Delta U=Q+W \quad \text{(IUPAC convention)}$$