[Physics] Distribution of charge on a hollow metal sphere

chargeconductorselectrostaticshomework-and-exercises

A hollow metal sphere is electrically neutral (no excess
charge). A small amount of negative charge is suddenly
placed at one point P on this metal sphere. If we check on
this excess negative charge a few seconds later we will find
one of the following possibilities:

(a) All of the excess charge remains right around P.

(b) The excess charge has distributed itself evenly over the
outside surface of the sphere.

(c) The excess charge is evenly distributed over the inside
and outside surface.

(d) Most of the charge is still at point P, but some will have
spread over the sphere.

(e) There will be no excess charge left.

Which one is correct and why?

I guess it is some kind of electrostatic induction – phenomena going on. Am I right? I understand that excess charge is distributed over hollow sphere and that negative and positive charges are distributed opposite sides, but don't know which one positive or negative go to inside surface.

Best Answer

Your homework question is from http://panda.unm.edu/Courses/Malloy/PHYS161//Physics_161_Home_files/Lecture22.pdf

Which one is correct

b)

and why?

  • Metal conducts.
  • Charges can travel freely in a conductor.
  • Like charges repel
  • The charge carriers move as far apart as they can be
  • The furthest apart they can be is evenly distributed over the outer surface.

See http://www.physlink.com/education/askexperts/ae28.cfm

I guess it is some kind of electrostatic induction - phenomena going on. Am I right?

I think not. See Wikipedia -"Electrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges"

I understand that excess charge is distributed over hollow sphere

The whole charge, not just some excess (over what?), is distributed over the sphere.

negative and positive charges are distributed opposite sides

No, if there were both positive and negative charges on opposite sides they would not stay there, they would be attracted to one another and quickly cancel out.

but don't know which one positive or negative go to inside surface.

Neither.

What is capacitors?

See Wikipedia re capacitors.

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