In figure, a sample of an ideal gas is taken through the cyclic process abca. `800J` of work is done by the gas during process ab. If gas absorb no heat in process ab, rejects `100J` of heat during bc and absord `500J` of heat during process `ca`. Then (a) find the internal energy of the gas at `b` and `c` if its is `1000J` at a (b). Also calculate the work by the gas during the part `bc`,

Explanation

(a) In process ab
`DeltaQ = DeltaU +W`
`Q = U_(B) - 100 +800`
`U_(B) = 200J`
for Cyclic process
`DeltaQ = DeltaU +W`
`400 = 0 +800 +W_(BC)`
`W_(BC) =- 400 J`
for process bc
`DeltaQ = DeltaU +W`
`- 100 =- 400 +U_(c) - 200 :. U_(c) = 500J`