Home

PHY 142: Electricity & Magnetism (Honors)
Prof. S. Teitel stte@pas.rochester.edu ---- Fall 2009

## Problem Set 5

Due Friday, October 16, by 2 pm in PHY 142 homework locker
• Problem 1 [5 points]

Purcell 3.1

• Problem 2 [10 points]

Purcell 3.4

• Problem 3 [10 points]

Purcell 3.8 - The outer planes connected by a wire means that they must be at the same electrostatic potential.

• Problem 4 [5 points]

Purcell 3.9 - Ignore the last two sentences of the problem. The geometry for the problem is as shown below. For the first part there are four charges, all equidistant from the x and y axes. For the second part there is one charge in front of a bent conducting plane as shown.

• Problem 5 [10 points]

Purcell 3.17 - This problem refers to a conducting sphere of radius b, surrounded by a conducting spherical shell of inner radius a.

Hint: The electric field between the conducting spheres is proportional to the charge Q on the inner sphere. The smaller is the radius of the inner sphere b, the smaller is the Q that can be put on the inner sphere and still satisfy the constraint E(b)=E0. For each b, there is thus a maximum Q that can be stored on the inner sphere. The energy stored in the capcitor is proportional to Q2. Your job is to find the b that allows the maximum energy to be stored.

• Problem 6 [10 points]

Purcell 3.23 part (a) only