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Triple point.

Radiation mode

\(\frac { C-0 }{ F-32 } \)
Let the temperature is x
∴ \(\frac { x }{ 5 } \) = \(\frac { x-32 }{ 9 } \)
9x = 5x – 5 × 32
x = \(\frac { 5\times 32 }{ 4 } \) = -40°C

λ_m T = b = 2.9 × 10^-3 mK.

S.I. unit of specific heat is J/Kg^-1 K^-1.
In C.G.S system unit is cal/gK.
In MKS system unit is Real/ KgK.
Molar unit of specific heat is cal mol^-1 K^-1.

Good emitters.

According to Wien’s displacement law λm T = b = 2.90 × 10^-3 mK.

That is on increasing the temperature λm moves towards the lower part of spectrum and when the temperature decreases, λm gets displaced towards the higher end of the spectrum. This is why it is called Wien’s displacement law.

1. In conduction, the heat transfer takes place at the molecular level without actual movement of molecules, from the hottest to the coldest surface.
2. In the process of heat transfer, the molecules pump into their neighbors and transfer the energy to them which continues as long as heat is still being added.
3. The transfer between bodies continues until the temperature difference decays and a state known as thermal equilibrium occurs.
4. Greater the value of thermal conductivity K of a body better is its heat conducting capability.
5. For insulator this value of K is zero.

Mercury is used in thermometer for the following reasons :

1. It does not stick to the walls of the tube.
2. It has high coefficient of expansion, hence the slightest change in temperature is notable.
3. It has a shiny surface, so it is easily visible.
4. It has high boiling point which makes it suitable to measure high temperature.

Temperature is a physical quantity that measures hotness or coldness of the body. The body that feels hot has a higher temperature than the body that feels cold. The device used to measure temperature is called thermometer.

We have experienced that a glass of ice cold water placed on a table (at room temperature) on a hot summer day eventually becomes warm; but a cup of hot coffee placed on the table cools down. So, an exchange of energy has taken between-water or coffee and the surrounding. This transfer of energy takes place till thermal equilibrium is reached.

So, temperature is that physical quantity of an object which tells whether an object is in thermal equilibrium with the other object or not. If the two objects kept in contact are not in thermal equilibrium, then heat will flow from object at high temperature to the object at lower temperature. When the temperature of both the objects becomes equal the heat flow stops. So, temperature is that physical quantity of an object which decides the direction pf flow of heat.

The S.I. unit of temperature is Kelvin and its value is \(\frac { 1 }{ 273.16 } \) point of water. Temperature is a scalar 273.16 quantity.

Other than kelvin scale, temperature can be measured in degree Celsius, fahrenheit, etc.

Heat : Heat is a form of energy. The hotness or coldness of any object is felt by it. When a hot object and a cold object are brought in contact with each other then the energy flows from hot to cold object. The energy transferred in this process is heat. The unit of heat is joule (J) or calorie. One calorie is defined as the quantity of heat energy required to raise the temperature of one gram (lg) of water from 14.5°C to 15.5°C.

• 1 Kcal = 10³ Calorie
• 1 calorie = 4.186 Joule.