(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?

Explanation

(a) This is because the comb gets charged by friction. If the hair are wet, or if it is a rainy day, friction between the hair and the comb reduces. The comb does not get charged, and it will not attract small bits of paper.
(b) The specail rubber tyres of air crafts are made slightly conduting so that electricity generated on account of friction between the tyres and the runway goes to earth.
(c) When a vehicle moves, its body gets charged on account of friction between the tyres and the road. The metallic ropes from the vehicle touching the ground enable the accumulated charge on account of friction between the tyres and the road = The metallic ropes from the vehicle touching the ground enable the accumulated charges to flow to earth. This would otherwise be hazordous to the inflammable materials.
(d) When a bird perches on single bare high power line, nothing happens to him as no current flows through his body. Current flows thorugh his body resulting in a fatal shock.