Laws of Thermodynamics HC Verma Solutions of Que for Short Ans Ch-26 Vol-2 Concept of Physics. Step by Step Solution of Questions for short answer of Ch-26 Laws of Thermodynamics HC Verma Question of Bharti Bhawan Publishers . Visit official Website CISCE for detail information about ISC Board Class-12 Physics.

## Laws of Thermodynamics HC Verma Solutions of Que for Short Ans Ch-26 Vol-2

 Board ISC and other board Publications Bharti Bhawan Publishers Ch-26 Laws of Thermodynamics Class 12 Vol 2nd writer H C Verma Book Name Concept of Physics Topics Solutions of Question for Short Answer Page-Number 60

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### Laws of Thermodynamics Que for Short Ans

HC Verma Solutions of Ch-26  Vol-2 Concept of Physics for Class-12

(Page – 60)

#### Question 1 :-

Should the internal energy of a system necessarily increase if heat is added to it?

Change in internal energy of a system, ΔU=CvΔT

Here,

Cv = Specific heat at constant volume

ΔT = Change in temperature.

If ΔT = 0, then ΔU = 0, i.e. in isothermal processes, where temperature remains constant, the internal energy doesn’t change even on adding heat to the system.

Thus, the internal energy of a system should not necessarily increase if heat is added to it.

#### Question 2 :-

Should the internal energy of a system necessarily increase if its temperature is increased?

Internal energy of a system increases if its temperature increases. This is valid only for the system of ideal gases and not for all the systems.

For example:- During meting process, temperature of the system remains constant, but internal energy change increases by mL.

⇒ ΔU = mL

Here,

m = Mass of the solid

L = Latent heat of the solid

#### Question 3 :-

A cylinder containing a gas is lifted from the first floor to the second floor. What is the amount of work done on the gas? What is the amount of work done by the gas? Is the internal energy of the gas increased? Is the temperature of the gas increased?

As a cylinder is lifted from the first floor to the second floor, there is decrease in the atmospheric pressure on the gas and it expands. Therefore, some work is done by the gas on its surroundings. Work done on the gas is zero.

Work done by the gas, W = PΔV (positive)

The increase in the internal energy and temperature of the system will depend on the types of the walls of the system (conducting or insulating).

#### Question 4 :-

A force F is applied on a block of mass M. The block is displaced through a distance d in the direction of the force. What is the work done by the force on the block? Does the internal energy change because of this work?

If force F is applied on a block of mass M and displacement of block is d, then work done by the force is given by

W = F.d = Fd cos(0°) = Fd

This work done does not change the internal energy of the block as the internal energy does not include the energy due to motion or location of the system as a whole.

#### Question 5 :-

The outer surface of a cylinder containing a gas is rubbed vigorously by a polishing machine. The cylinder and its gas become warm. Is the energy transferred to the gas heat or work?

As the outer surface of a cylinder containing a gas is rubbed vigorously by a polishing machine, no work is done on the cylinder. Volume of the gas remains constant and the heat energy generated due to friction between the machine and the cylinder gets transferred to the gas as heat energy. This heat energy leads to an increase in the temperature of the cylinder and its gas.

— : End of Laws of Thermodynamics HC Verma vol -2 Que for Short Ans :–