Coulomb’s Law Questions
1.
A helium nucleus has charge +2 e and a neon nucleus +10 e , where e =
1.60 x 10
-19
coul. With what force do they repel each other when separated by 3 x 10
-9
meters?
2.
If two equal charges, each of 1 coulomb, were separated in air by a distance of 1 km, what would be the force between them?
3.
Determine the force between two free electrons spaced 1 angstrom (10
-10
m) apart.
4.
What is the force of repulsion between two argon nuclei when separated by 1 millimicron (10 -9 m)? The charge on an argon nucleus is +18 e .
5.
Two equally charged pith balls are 3 cm apart in air and repel each other with a force of 4 x 10 -5 N. Compute the charge on each ball.
6.
Two small equal pith balls are 3 cm apart in air and carry charges of +3 x 10
-9
and
–12 x 10 -9
C respectively. Compute the force of attraction. If the balls are touched and then separated by a distance of 3 cm, what will be the force between them?
7.
The normal hydrogen atom consists of a proton nucleus and an orbital electron, each carrying the fundamental charge of magnitude e = 1.60 x 10 -19 C. Assuming that the electron orbit is circular and the separation between the particles is 5.3 x 10
-11
meters, find: a) the force of electrical attraction between the particles b) the gravitational force of attraction between them c) which force is larger? How many times?
(mass e- = 9.11 x 10 -31 kg ; p+ = 1.67 x 10 -27 kg)
8. +5 e
2 cm
-4 e
1 cm
What is the net force on the sphere having charge of –4 e ?
+2 e
9.
Charges of +2, +3 and –8 microcoulombs are placed in air at the vertices of an equilateral triangle of side 10 cm. Calculate the magnitude of the force acting on the
-8
 c due to the other two charges.
(1 microcoulomb (1
 c) = 1 x 10
-6
C)

Answers for Coulomb’s Law Questions
1.
5.1 x 10 -10 N
2.
8930 N repulsion
3.
2.3 x 10 -8 N repulsion
4.
7.4 x 10 -8 N
5.
2 x 10 -9 C
6.
a) 3.6 x 10
–4
N
7.
a) 8.14 x 10 -8 N b) 2 x 10 -4 N repulsion b) 3.61 x 10 -47 N c) Electrical force 2.25 x 10 -47
8. Fnet = 2.16 x 10 -23 N L58

D
times greater
9. 31.1 N