Question

Why the work done by the system is always negative in expansion

Answer 1

Dear Student,

The work done by the system is always negative in expansion, because work is done by the system. Work done is given by:
w = -P$∆$V
P = pressure
$∆$V = difference in volume = V_f - V_i
V_f = final volume
V_i = initial volume
In an expansion, final volume is more than V_i, so ​$∆$V is positive. So, final work is negative.

Regards