A cylinder of ideal gas is closed by an 8kg movable piston of area `60cm^2`. The atmospheric pressure is 100kPa. When the gas is heated form `30^@C` to `100^@C`, the piston rises 20 cm. The piston is then fastened in the place and the gas is cooled back to `30^@C`. If `DeltaQ_1` is the heat added to the gas during heating and `DeltaQ_2` is the heat lost during cooling, find the difference.

Answer

A, C

Explanation

First process is isobaric.
`:.` `DeltaQ_1=nC_VDeltaT+pDeltaV`
Second process is isochoric.
`:.` `DeltaQ_2=nC_VDeltaT`
`DeltaQ_1-DeltaQ_2=pDeltaV=[p_0+(mg)/(A)][Ax]`
`=(p_0A+mg)x`
`=[10^5xx60xx10^-4+8xx10](0.2)`
`=136J`