- #1

echau

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Charge is distributed on a long, straight rod with uniform density 6.5 x 10^-8 C/m. Compare the magnitude of the field 1 cm from the rod to the field 1 cm from a point charge q = 6.5 x 10^-8.

The answer in the back of the book is: E(rod)/E(point)=.02=2%

I was thinking that the Electric fields would be the same since the charge is the same, but then I realized that the charge is spread out on the rod. How would I find the Field for the rod to solve the problem? I'm assuming that for the point charge it's just kq/r^2 = [(8.99 x 10^9)(6.5 x 10^-8)]/(.01^2).

The second problem is regarding motion.

Consider a solid sphere of radius

*R*with a charge

*Q*distributed uniformly. Suppose that a point charge

*q*of mass

*m*, with a sign opposite to that of

*Q*, is free to move within a solid sphere. Charge

*q*is placed at rest on the surface of the solid sphere and released. Describe the subsequent motion. In particular, what is the period of the motion, and what is the total energy of the point charge? [

*Hint:*recall the properties of the motion for which the force varies linearly with the distance from a fixed point and is a restoring force.]

If anyone could help me with either of these two problems, I would greatly appreciate it. Thank you!