Forces and Field Concept Check 5 Solutions
Concept:
1.
Explain, qualitatively, the principles pertinent to Coulomb’s torsion balance
experiment
Coulomb determined the relationship between electric forces and the product of the
charges. What is this relationship?
It is a direct relationship. What happens to one happens to the other. i.e. If the charge
of one object is halved, the electrical force is also halved.
2.
Coulomb based his experiment on those done by Cavendish. What force did they use to
balance the forces of attraction or repulsion the objects present in their experiments
experienced.
Both their experiments caused either the gravitational or electric forces to twist a wire. A
twisting force is called torsion. Therefore, they would have used a torsional force to
balance and therefore measure the electrical and gravitational forces.
3.
The electrical force of repulsion between two charges is 100 N. What will be the force of
repulsion after each change occurs. (after each change go back to original charges)
a.
b.
4.
one charge is doubled (200N)
one charge is tripled and the other halved. (150N)
Coulomb determined the relationship between electric forces and the distance separating
their centre of masses. What is this relationship?
It is an inverse square relationship. What happens to one, the inverse squared happens
to the other. i.e. If the distance is halved the electrical force is double squared or four
times larger.
5.
The electrical force of repulsion between two charges is 100 N. What will be the force of
repulsion after each change occurs. (after each change go back to original charges)
a.
b.
c.
the distance between the charges is tripled. (11.1 N)
the distance between the charges halved. (400 N)
the distance between the charges is doubled and each charge is doubled. (100N)