Electricity and Magnetism

E

Electric Field and Potential Problems

Useful Data

Unless otherwise specified, here and throughout the other collections of problems we employ

the following conventions.

SI Times are measured in seconds, s, distances in metres, m, masses in kilograms,

kg, forces in newtons, N, and angles in radians, rad.

e The quantum of elementary charge is e ≃ 1.6 × 10

−19

C.

k Coulomb’s constant has the approximate value k ≃ 8.99 × 10

9

N·m

2

/C

2

. Here

we shall use k = 9 × 10

9

for simplicity.

ǫ

0

The permittivity of free space is ǫ

0

= (4 π k)

−1

≃ 8.85 × 10

−12

C

2

/( N·m

2

).

m The electron mass is m

e

≃ 9.1 × 10

−31

kg. The proton mass is m

p

≃ 1.67 ×

10

−27

kg. The atomic mass unit is 1