please explain the sign conventions regarding work done in the 1st law expression in detail.please include p-v graphs and sign convention related to this in the discussion.i am really confused about this.thank you very much!

Dear tushar

If the work is done by system then it is positive and if work is done on the system them work done will be negative

lets discuss with carnot cycle.

in compression process work is done on the system so work done will be negative.(4-1)

in expansion process work is done by the system so it will be positive.(2-3)

lets find the magnitude of work done

We =+Cv(T2-T3)

it will be positive

and

Wc = -Cv(T1-T2)  we have taken - sign becouse work done is negative

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