In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

A white powder is added while baking bread and cakes to make them soft and fluffy. Write the name of the powder. Name its main ingredients. Explain the function of each ingredient. Write the chemical reaciton taking place when the powder is heated.

A spherical conducting shell of inner radius r_(1) and outer radius r_(2) has a charge Q. (a) A charge q is placed at the centre of the shell. What is the surface charge density on the inner and outer surfaces of the shell? (b) Is the electric field inside a cavity (with no charge) zero, even if the shell is not spherical, but has any irregular shape? Explain.