Important Terms

The mode of transfer of heat by vibrating atoms and free electrons in solids from hotter to a colder part of a body is called the conduction of heat.

The amount of heat that flows in unit time is called the rate of flow of heat.

The rate of flow of heat across the opposite faces of a meter cube maintained at a difference of 1 K is called the thermal conductivity of the material of the cube.

Transfer of heat by actual movement of molecules from a hot place to a cold place is known as convection.

Radiations from the Sun pass easily through glass/polythene and warms up the materials inside a greenhouse. The radiations given out by them are of much longer wavelengths. Glass/polythene does not allow them to escape out and thus maintains the inside temperature of the greenhouse.

A thermos flask consists of a double-walled glass vessel. It reduces the transfer of heat by conduction, convection, and radiation.