Learn more physics!
Why is it difficult to charge a metallic rod by just rubbing it with cloth?
- Krizia (age 16)
Augustinian Abbey School, Philippines
I bet that the biggest problem is that the chrage can flow very easily through the metal and fairly easily through you. That lets it drain away. Maybe if you held the rod with a thick cloth glove, it would be insulated enough to charge up.
I'll bet there's also a problem even in the friction contact. Electrons have to be transferred from one of the objects to the other. The oppositely charged rod and cloth will attract, and the electrons will like to recombine with the positively charged object. I'll bet that in the rubbing process which charges insulators (like balloons or plastic), it is important that electrons cannot flow to go back and recombine with the positively-charged places where they came from.
(republished on 07/13/06)
Follow-up on this answer.