The `P-V` diagram of a system undergoing thermodynnaic transformation is shown in Fig. The work done on the system in going from `A rarr B rarr C` is `50 J` and `20 cal` heat is given to the system. The change in internal erergy between `A` and `C` is

Options

A. `34 J`
B. `70 J`
C. `84 J`
D. `134 J`

Answer

D

Explanation

d. Heat given, `Delta Q`
`= 20 cal = 20 xx 4.2 = 84 J`
Work done `Delta W = - 50 J`
as the process is anticlckwise
By the first law of thermodynamics,
`Delta U = Delta Q - Delta W = 84 - ( - 50) = 134 J`