Source: High school physics (Chinese)
Problem Sets:
Problem
A person is holding a metal rod.
- Why does the metal rod not accumulate a net charge when rubbed?
- How can the metal rod be given a net charge?
The rod is grounded through the body; Insulate the rod from the hand.
[Q1] Both the metal rod and the human body are electrical conductors. When the person holds the rod, any charge transferred to it by rubbing immediately flows through the person to the Earth, which acts as a vast reservoir for charge. The rod is effectively grounded, preventing charge accumulation.
[Q2] To charge the rod, it must be electrically insulated from the person's hand and the ground. This can be achieved by holding the rod with an insulating material, such as a rubber glove or a plastic handle. Once insulated, it can be charged by methods like friction or induction.