Physics 2003 JAMB Past Questions - Question 27: A positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place. When the finger is removed, the result is that Y has

Correct Answer

E

Explanation

When a positively charged rod X is brought near an uncharged metal sphere Y and is then touched by a finger with X still in place, the following series of events occur:

1. Initially, the uncharged metal sphere Y is neutral.

2. When the positively charged rod X is brought near sphere Y, it induces a separation of charges in sphere Y due to electrostatic induction. Electrons in the metal sphere Y are repelled by the positively charged rod X, causing the electrons to move away from the side of Y closest to X and accumulate on the side farthest from X. This creates a temporary charge separation within Y.

3. When you touch sphere Y with your finger while the positively charged rod X is still nearby, some of the excess electrons from the side of Y farthest from X will transfer to your finger, which is an electrical conductor. This causes sphere Y to lose some of its excess electrons and, as a result, it becomes positively charged.

4. When you remove your finger and the positively charged rod X, sphere Y remains positively charged because it lost electrons during the process of touching with your finger.

So, after the process, sphere Y will be positively charged.