An ideal gas is taken through the cycle `AtoBtoCtoA,` as shown in the figure, If the net heat supplied to the gas in the cycle is 5J, the work done by the gas in the process CtoA is

Options

A. `-20 J`
B. `-5J`
C. `-10J`
D. `-15J`

Answer

B

Explanation

(1) A to B is an isobaric process where P is kept constant.
The work done `W_(AB)=PdV=P(V_(2)-V_(1))`
`=10(2-1)=10J`
(2) B to C is isochoric for which V = constant
`therefore`W = PdV = 0
The heat supplied dQ = 5J
as this is a cyclic process, dU = 0
and dQ = dW = 5J
`thereforedW=W_(AB)+W_(BC)+W_(CA)`
`therefore5J=10+0+W_(CA)" "thereforeW_(CA)=-5J`