PHYS208 Fundamentals of Physics II

Hint for Ch. 24, 20E

a) Consider a gaussian surface which is just outside the inner surface of the spherical shell. E is zero everywhere on that surface.

b) E remains zero on the surface of part a). Can there be any change?

c) E must still remain zero on the surface of part a).

d) What would make them change?

Hint for Ch. 24, 27P

Use a cylindrical gaussian surface, coaxial with the actual cylinders. Remember that the electric field is everywhere zero in a conductor.

Hint for Ch. 24, 53P

At all points where there is an electric field it is radially outward. For each part of the problem use a spherical gaussian surface, centered about the center of the actual spheres, and passing through the point where the field is to be found.

a) Charge enclosed is q (r/a)3 for r < a.

b) Charge enclosed is q for a < r < b.

c) The shell is conducting.

d) Charge enclosed is zero.

e) For b < r < c , the electric field must be zero; a gaussian sphere with this radius must enclose no net charge.

Hint for Ch. 25, 77E

a) So what exactly does the conducting wire do when it joins the other two conductors -- think electrostatics!

b) Use the result for the potential on a spherical conductor, V = kq/R.

c) Use the results of part b) for each sphere.

Last updated March 5, 1998.
Copyright George Watson, Univ. of Delaware, 1997.