Question

Heat from the sun reaches the earth.

1. Write the method of transmission of heat.

2. Thermal conductivity of Aluminium is 205 Jm^-1s^-1deg^-1. What do you mean by this?

3. Birds swell feathers in winter. Why?

Answer 1

1. Radiation, conduction, convenction.

2. The coefficient of thermal conductivity of a substance is defined as the quantity of heat conducted normally per-second through unit area of the substance per unit temperature gradient when the substance attains steady state.

3. By doing so the birds enclose air between the feathers. Air being a poor conductor, prevents the loss of heat from the body of the bird to the cold surroundings.