Question

A hard rubber rod is rubbed with wool and thus gains an approximately uniform net negative charge. The rubber rod is then suspended from a plastic string. A neutral (net charge zero) copper rod is also suspended from a plastic string and brought near the rubber rod. The rods never touch, and no spark jumps between the rods. The rubber rod and the plastic string are insulators (i.e., charge is not free to move through them). The copper rod is a conductor (i.e., charge is free to move through it).

Which of the following best represents the charge distribution on the acrylic rod after the rubber rod is moved far away from the acrylic rod? 1) No charge 2) positive charge at the end it was rubbed on 3)negative charge at the end it was rubbed on 4) positive charge throughout 5) Negative charge throughout 6) Negative at one end and positive at the other Is the net charge on the acrylic rod positive, negative, or zero? When the rubber rod was scraped, the net charge on the rubber rod changed or remained the same?

Answer 1

The acrylic rod gains a net negative charge by coming in contact with the hard rubber rod. This is because when brought in contact with the rubber rod some of the excess electrons which are responsible for the negative charge on the rubber rod gets deposited on the acrylic material. Electrons generally will be deposited more on a body where there is more space to accommodate them. So the magnitude of charge that gets deposited on the acrylic material depends on the free sites available to the incoming electrons.

Step-by-step explanation:

When the rubber rod is scrapped the net charge on the rubber rod changes to positive or negative depending on if it is gaining or loosing electrons. The act scrapping happens because of friction and friction causes transfer of charges between two different materials. The material that loses electronic gains a net positive charge and the material that accepts gains a net negative charge.