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

## Problem Set 7

Due Monday, November 2, by 2 pm in PHY 142 homework locker

You may have to wait for Tuesday's lecture to do many of these problems

• Problem 1 [5 points]

Consider a square loop of side a, with current I1, sitting a distance d awary from an infinite straight wire with current I2 as shown in the picture below. What is the net force on the loop due to the magnetic field of the wire. Consider both the case where I1 > 0 (current clockwise as shown) and I1 < 0 (current counter-clockwise, opposite as shown). Be sure to give the magnitude and direction of the force.

• Problem 2 [10 points]

a) Consider two infinite flat planes separated by a distance d. The planes are oriented with normal in the z direction. If the top plane has a uniform surface current density K in the x direction, and the bottom plane has a uniform surface current - K in the x direction, find the magnetic field everywhere above, below, and in between the two planes. What if the bottom plane has surface current +K in the x direction? What if the bottom plate has surface current K in the y direction?

b) Consider an infinite flat plane of finite thickness d. The plane is oriented with normal in the z direction. A uniform current density J is distributed throughout the cross-sectional area of the plane. Find the magnetic field above, below, and inside the plane.

• Problem 3 [10 points]

Purcell 6.16 - assume the current is distributed uniformly over the cross-sectional area of the rod.

• Problem 4 [10 points]

Purcell 6.3

• Problem 5 [10 points]

Purcell 6.4

• Problem 6 [5 points]

Purcell 6.12