Help needed in electric field

Can someone explain Question 5 to me please.


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It's asking you to consider the electric forces between the positively charged rod lowered into the can, and the charges on the inner surface of the can.

Several things to remember:

1) Electrons (-ve charges) are free to move between atoms but protons are fixed and non-movable.

2) The can is standing on a conductive surface directly in contact with the earth.

3) Consider the earth as an infinite source or sink of electrons.

4) Like charges repel, unlike charges attract.

Then consider what happens to electrons on the surface of the can as the positively charged (more protons than electrons) rod is lowered into the can. Do the electrons on the can stay in position or do they move? If they move and their parent protons stay in the same position, what happens to the net charge distribution on the surface of the can?

The electric field is a diagram of the distribution of the electric force lines acting between the rod and the can.

Remember that the separation distance between the force lines represents the strength of the electric field at that position. The wider apart, the less the field strength. Most importantly, remember that the field strength (force acting at any given point) is also a function of distance between the charges.