Diatomite

Diatomaceous earth :Silica shell of dead diatoms are nearly indestructible and thus, get accumulated at the sea bed. Such huge rock like deposits of hard shell of diatoms constitutes earth, which is mined to obtain a whitish powder called diatomites or Kieselguhr.

Diatomites are rough and gritty. Because of these features, it is used in filters in brewing industry, sugarcane refineries, in metal polishing, toothpaste, for making insulating bricks, water glass or sodium silicates and strong acids.

This is added to paints to increase their night visibility. The common example of diatoms are Triceratium, Pleurosigma, Navicula, Cymbella.

                                                                               https://youtu.be/UCHIvvAvekA

Thermodynamics equilibrium

Thermodynamics equilibrium : A system in which the state variables have constant values throughout the system is said to be in state of thermodynamics equilibrium.

The criteria for equilibrium :

1) The temperature of the system must be uniform and must be same as the temperature of the surrounding (thermal equilibrium).

2) The mechanical properties of the system must be uniform throughout the system (mechanical equilibrium). That is no mechanical work is done by one part of the system on any other part of the system.

3) The chemical composition of the system must be uniform with no net chemical changes (chemical equilibrium).

                                                                                                     https://youtu.be/UCHIvvAvekA

Negative temperature

Negative temperature : A part from the system i.e., the nucleus of a solid can have a negative temperature. This sub-system is considered isolated from the main system.

The specific heat of the subsystem tends to zero at high temperature. A small amount of heat energy tends to raise the temperature of the sub-system to infinitely. It is possible to add still more energy to the sub-system at infinity and force the sub-system into the negative temperature region.

          The negative temperature are hotter than the positive temperature. (-0) is the hottest temperature and (+0) is the coldest temperature.

                                                                          https://youtu.be/UCHIvvAvekA

second law of thermodynamics

Second law of thermodynamics :  The law specifying the condition of transformation of heat into work is called the Second law of thermodynamics.

There are several statements which explains the second law of thermodynamics ------

1) Kelvin-Planck's statement : It is impossible to construct an engine, operating in a cycle, to extract heat from hot body and convert it completely into mechanical work done i.e., 100% conversion of heat into work is impossible.

2) Clausius statement : It is impossible for any cyclic machine to produce no any effect other than to convey heat continuously from one body to another at a higher temperature.

3) Kelvin's statement : It is impossible to get continuously supply of work by cooling a body to a temperature lower than that of the coldest of its surroundings.

                                                  

                                                                                                              https://youtu.be/UCHIvvAvekA 

Third law of thermodynamics

Third law of thermodynamics :- There are several statements for third law of thermodynamics:

1) Nernst statement : The heat capacity of a solid tends to zero, as the absolute zero of temperature approached and the internal energies and entropy of all the substances becomes equal there, approaching common value asymptotically.

2) Planck's statement :  The entropy of every actual substance in the pure state is zero at the absolute zero temperature.

3) Fowler and Gauggenheim's statement : It is impossible by any procedure, to reduce a system to absolute zero temperature in a finite number of operation.

                                                                   https://youtu.be/UCHIvvAvekA

Kinetic Theory of gases

 Kinetic Theory of Gases :-

• Gases consist of large number of molecules.
• Molecules of gases are always in random motion.
• The volume of a gas molecule is negligible as compared to the total volume occupied by the gas.
• During random motion molecules of gas collides with each other and with the walls of the container.
• The collision of the gas molecules are perfectly elastic. There is no loss in kinetic energy and the total momentum remains conserved.
• The momentum transfer by the molecules of the gas during collision on the surface of the container is called as PRESSURE exerted by the gas.
• Intermolecular  forces are negligible except during the collision of molecules.
• A molecule moves with uniform velocity during collisions{ignoring gravity}.

                                                                                                                 https://youtu.be/O3D2belxKBs

torsional pendulum

 Torsional Pendulum:

 In torsional pendulum, an extended body is suspended by a light thread or wire. The body is rotated through an angle about the axis of rotation.

The wire remains vertical during this motion but twist Ө  is produced in the wire. The twisted wire exerts a restoring torque on the body, which is directly proportional to the angle of twist 

                                 τ α –θ

                                 τ = -k θ   

where k is the proportionality constant called torsional constant of the wire.

If I be the moment of inertia of the body about the vertical axis, then the angular acceleration of the body will be -------

     As we know,            τ = I α

                                     α = τ/I
                                     α = –kθ/I
                                     α = –ω2θ
Therefore,                    ω2 = k/I

                                             ω = (k/I)^1/2    

     As we know,                   T = 2π/ω   

                                             T = 2π(I/k)^1/2     

                                                                      https://youtu.be/O3D2belxKBs