Two cylinders A and B fitted with pistons contain equal amount of an ideal diatomic gas at 300 K. The piston of A is free to move, while that of B is held fixed. The same amount of heat is given to the gas in each cylinder. If the rise in temperature of the gas in A is 30K, then the rise in temperature of the gas in B is

Heat is given to the gas in cylinder A at constant pressure while the same amount of heat is given to the gas in cylinder B at constant volume. Heat given to gas in A is              QA=nCpΔTA              Heat given to gas in B is QB=nCυΔTB              Since QA=QB,  we have             nCpΔTA=nCυΔTB              Or                    ΔTB=CpCυΔTA=75×30  K=42  K                  (∵  For a diatomic gas, Cp/Cυ=7/5 )