Question:
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U = q + w
Change in internal energy is due to heat change and work
If work is done on the system then it is positive sign
If work is done by the system then it is negative sign.
By definition W = -P ∆V
∆U = ∆q -P ∆V
∆U = ∆q + W
None of the option is correctly fitted here.
During expansion - work is done by the system
∆U = ∆q - W[/b][/color]
During compression work is done on the system
∆U = ∆q + W[/b][/color]