05-01-2018, 04:52 PM
*Rail Road tracks are constructed in such a way that they can safely expand on a hot day without derailing when the train is travelling over them.
* When the temperature increases the length of the electric lin e between 2 towers increases and line sags.
Thermal Conductivity
*The property of a material to conduct heat is called as - Thermal Conductivity.
*Thermal conductivity of a material depends on temperature.
*Unit (SI) of thermal conductivity. - watts per ... meter kelvin (W/mk)
*The law of heat conduction is called -Fourier’s law.
*Coefficient of thermal conductivity is. also known as - K factor or thermal admittance.
*Newton’s Law of Cooling : This law states that the rate at which a hot body loses heat is directly proportional to the difference between its temperature and the ‘Surrounding temperature.
*If hot water and fresh tap water are kept in a refrigerator, the rate of cooling of hot water will be faster than the tap water.
* In a refrigerator cooling is produced by the evaporation of a volatile liquid, Freon inside a copper coil which surrounds the freezer.
*The amount of water vapour present in air is called humidity.
*Perspiration is maximum, when temperature is high and air is humid.
*The exerted pressure reduces the melting point of ice. This phenomenon is known as regelation.
*Skating on ice is possible due to the phenomenon of regelation.
*Joule’s law is related to the heat.
*Joule’s law of heating states that the heat produced in a conductor is directly proportional to the square of current (I) flowing through the conductor; resistance ® of the conductor and time (t) for which the current is passed.
H = I^2 Rt
*Mica is a good conductor of heat even though it is a bad conductor of electricity.
*The density of a body decreases with rise in temperature.
*According to the Principle of Calorimetry, heat lost by the hot body is equal to the heat gained by the cold body at thermal equilibrium.
Melting point and Boiling point
*The fixed temperature at which solid becomes a liquid at standard atmospheric pressure is called
Ans : Melting Point.
*Melting point of ice can be raised by the decrease of pressure:
*The fixed temperature at which a liquid boils and changes itself into vapour at standard atmospheric pressure is called
Ans : boiling point.
*The boiling point of water increases with increase in pressure.
*Water inside a Pressure Cooker boils at a temperature of 120° C as the boiling point of water increases with increase in pressure.
Info Plus
*Melting point of Mercury is - 39^0C
*Melting point of Alcohol is - 114^0C
