# Rutgers Physics 385 Electromagnetism I (Fall'15/Gershtein)

## Homework 1 - Due September 10, 2015 in class

"Griffiths" refers to the textbook Introduction to Electrodynamics, 4th Edition, by David J. Griffiths

1) Do the integral

2) Griffiths, Problem 2.2:
Find the electric field (magnitude and direction) a distance z above the midpoint between equal and opposite charges (+q and -q), a distance d apart.

Also do the case for z=0.

3) Griffiths, Problem 2.5:
Find the electric field a distance z above a center of a circular loop of radius r that carries a uniform line charge λ

Express the answer in terms of the total charge on the ring and do the cases for very small and large z. How do they compare to the inverse-square law? Why?

4) Griffiths, Problem 2.7:
Find the electric field a distance z from the center of a spherical surface of radius R that carries a uniform charge density σ . Treat the case z < R (inside) as well as z > R (outside). Express your answer in terms of total charge q on the sphere.

This can be done many ways, but see if you can use the results of your solution of 2.5