Explanation:

When a metal rod is rubbed with wool, electrons are transferred from the metal to the wool due to the triboelectric effect. However, since the metal is a good conductor, the electrons quickly spread out throughout the metal and neutralize any charge. Therefore, the metal rod does not show any signs of being charged.

On the other hand, if a metal rod has a wooden or plastic handle and is rubbed without touching its metal part, the electrons cannot spread out throughout the metal due to the insulating properties of the handle. This causes a buildup of charge on the metal part of the rod, resulting in signs of charging.

The process of charging a metal rod with a wooden or plastic handle can be explained in more detail using the following headings:

1. Triboelectric effect
When two materials are rubbed together, electrons can be transferred from one material to the other due to differences in their electron affinity. In the case of rubbing a metal rod with wool, electrons are transferred from the metal to the wool, leaving the metal positively charged and the wool negatively charged.

2. Conductivity of metals
Metals are good conductors of electricity since electrons can move freely through them. When the metal rod is charged due to rubbing with wool, the electrons quickly spread out throughout the metal, neutralizing any charge. Therefore, the metal rod does not show any signs of being charged.

3. Insulating properties of wooden or plastic handles
Unlike metals, wood and plastic are insulators, which means that they do not allow electrons to move freely through them. When a metal rod with a wooden or plastic handle is rubbed without touching its metal part, the electrons cannot spread out throughout the metal due to the insulating properties of the handle. This causes a buildup of charge on the metal part of the rod, resulting in signs of charging.

Conclusion:

In conclusion, charging a metal rod with a wooden or plastic handle is possible due to the insulating properties of the handle, which prevent the electrons from spreading out throughout the metal. This causes a buildup of charge on the metal part of the rod, resulting in signs of charging. However, a metal rod held in hand and rubbed with wool will not show any signs of being charged due to the conductivity of metals.