Le Fevre High School
SACE Stage 2 Physics
Electric Fields 1
1.
(a) State Coulomb's Law.
(b) Find the electrostatic force between charges of +2.0 C and +5.0 C separated by a distance
of 75 m in a vacuum.
2
Two charges of +8.0 mC and -6.0 mC attract each other with a force of 3.0 x 103 N in a
vacuum. What is the distance between the charges?
3
A metal sphere of mass 6.0 x 10-3 kg is found to just float in air above a similar metal sphere
when both have a charge of 4.0 mC. Assuming that the only upwards force is electrostatic
repulsion, find the distance between the spheres.
4.
A charge of 12 C when placed in an electric field experiences a force of 648 N. What is the
magnitude of the electric field strength?
5.
Compare the magnitude of the electrostatic repulsion with the magnitude of the force of
gravitational attraction between two electrons 0.01 cm apart.
6.
Two small charged spheres have their centres 0.05 m apart and repel each other with a force of
5 x 10-5 N.
(a) What would be the force of repulsion if the spheres were 0.10 m apart?
(b) What would be the force of repulsion if the spheres were 0.025 m apart?
(c) What would be the force at 0.05 m separation if the charge on one of the spheres was
reduced by a half?
7.
Find the magnitude and direction of the force on a charge of +10 C placed at X in each of the
following:
(a)
+5C
+5C
X
1.5 m
1.5 m
(b)
+5C
2m
+5C
X
1m
(c)
X
1.0 m
+5  C
+5  C
1.0 m
1.0 m
Le Fevre High School