Question

Work done by a system is taken to be
a) positive
b) negative
c) zero
d) varies according to situation

Answer 1

If you use the notation of 1st law as follows:

Q - W = dE

then,

if system is expanded ( i.e. system DOES work on the surroundings) then, W must be positive

b)

If we use the notation

Q + W = dE

then,

the System is losing energy, due to the expansion, so we must account this as NEGATIVE.

Therefore, vaeries according the situation

Typically, modern thermodynamics courses use the first notation

Q - W = dE

then, the Work done must be accounted possitive

choose A