Question

If you hold a plastic comb in your hand and rub it in your hair it will get charged however if you do the same with a metal come it will not get charged why

Answer 1

Metals are a good conductor of electricity. They cannot hold static charges as charges keep flowing through them, our body and then ultimately down to earth. Plastic, on the other hand, is an insulator which can keep static charge build up. This is why it attracts pieces of paper and a metal wouldn't (as it has no static charges all have travelled down)

Answer 2

 Both plastic and metal comb will get charged when rubbed in the hair. However, since metal is a conductor, the charges will flow to earth through the body and it will lose its charge. If the metal comb has an insulating plastic handle it will retain its charge.