A metal rod held in hand and rubbed with wool will not show any sign of being charged. However, if a metal rod with a wooden or plastic handle is rubbed without touching its metal part, it shows signs of charging: Explain Why?

When a metal rod is held in hand and rubbed with wool, it may not show signs of being charged because the human body can act as a conductor and help dissipate any excess charge that might accumulate on the metal rod. Metals are generally good conductors of electricity, so if the rod is in direct contact with your hand, any charge generated during the rubbing process can quickly flow through your hand and into the ground, neutralizing the rod's charge. As a result, you may not observe any significant signs of charging.

However, when a metal rod with a wooden or plastic handle is rubbed without touching its metal part, it can show signs of charging. This happens because the handle of the rod is an insulator, which means it does not conduct electricity very well. When you rub the rod against wool, friction between the two materials can transfer electrons from one to the other, leading to an accumulation of charge on the metal part of the rod. Since the handle is an insulator, it does not provide a pathway for the excess charge to escape, so it remains localized on the metal part.

This localized charge on the metal part of the rod can lead to observable signs of charging, such as attracting small lightweight objects like pieces of paper or causing a spark when brought close to a conductor. The insulating handle prevents the charge from dissipating, allowing you to see the effects of the accumulated charge more easily.

In summary, the difference in the ability to conduct electricity between the human body (which acts as a conductor) and the insulating material of the handle (which acts as an insulator) determines whether a metal rod shows signs of charging when rubbed with wool.