The electric charge in uniform motion produces

What type of charges are obtained on silk cloth and glass rod ?

$(a)$ A comb run through one’s dry hair attracts small bits of paper. Why?

    What happens if the hair is wet or if it is a rainy day? (Remember, a paper does not conduct electricity.)

$(b)$ Ordinary rubber is an insulator. But special rubber tyres of aircraft are made slightly conducting. Why is this necessary?

$(c)$ Vehicles carrying inflammable materials usually have metallic ropes touching the ground during motion. Why?

$(d)$ A bird perches on a bare high power line, and nothing happens to the bird. A man standing on the ground touches the same line and gets a fatal shock. Why?

Write definition of unit Coulomb.

What is called polarity of electric charge ?

Five balls numbered $1$ to $5$ are suspended using separate threads. Pairs $(1, 2)$, $(2, 4)$ and $(4, 1)$ show electrostatic attraction, while pair $(2, 3)$ and $(4, 5)$ show repulsion. Therefore ball $1$ must be