One mole of an ideal diatomic gas undergoes transition from A to B along a path AB as shown below.

The change in internal energy of the gas during the transition is

Assertion : It is hotter over the top of a fire than at the same distance on the sides.

Reason : In the upward direction, the heat propagate through convection.

Assertion : In adiabatic expansion the product of $$p$$ and $$V$$ always decreases.

Reason : In adiabatic expansion process, work is done by the gas at the cost of internal energy of gas.

Assertion : The molecules of a monoatomic gas has three degrees of freedom.

Reason : The molecules of diatomic gas has five degrees of freedom.