Let's charge a conductor (we'll use an electroscope) by touching it with a charged insulating rod at one spot. Is there a more effective way to charge the electroscope?

1. Rubbing the rod over the electroscope is better
2. Electrically connecting the rod and the electroscope with a wire is better
3. It depends whether the insulating rod has + charge or - charge
4. No - because the electroscope is a conductor touching and rubbing are equivalent

If the charged object is an insulator, touching it to the conductor transfers charge only at the few points of contact. Rubbing the insulator over the conductor is much more effective at transferring charge. It makes no difference whether the rod has a positive charge or a negative charge.

The conductor acquires charge of the same sign as the charged object brought into contact with it.