Question

This problem explores the behavior of charge on realistic (i.e. non-ideal) insulators. We take as an example a long insulating rod suspended by insulating wires. Assume that the rod is initially electrically neutral. For convenience, we will refer to the left end of the rod as end A, and the right end of the rod as end B (Figure 1). In the answer options for this problem, "weakly attracted/repelled" means "attracted/repelled with a force of magnitude similar to that which would exist between two balls, one of which is charged, and the other acquires a small induced charge". An attractive/repulsive force greater than this should be classified as "strongly attracted/repelled".

After several contacts with the charged ball, how is the charge on the rod arranged.

Select the best description.

positive charge on end B and negative charge on end A

negative charge spread evenly on both ends

negative charge on end A with end B remaining almost neutral

positive charge on end A with end B remaining almost neutral

none of the above

How does end A of the rod react when the ball approaches it after it has already made several contacts with the rod, such that a fairly large charge has been deposited at end A?

Select the expected behavior.

strongly repelled

strongly attracted

weakly attracted

weakly repelled

neither attracted nor repelled

Answer 1

Diagram:

At the first time, when negative charged sphere touches end A, there induces a postive charge and negative charged at end B. As rod is insulator here, charge flow is reserved and small charge is induced at end A.

As it touches several times, large negative charge is deposited at end A. Because,the flow of charge is inhabitated in insulators, charge flow through rod is very less and more negative charge depoistied at end A and end B is neutral.

Therefore, negative charge on end A with end B remaining almost neutral.

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As the rod acquired a negative charge at end A after touch several times, the ball will be repelled. As the charge deposited at A is large, the ball will strongly repelled.