Module 1: Electric Charge, Force, and Field

Question 1

Answer 1

Question 2

A proton and an electron are held apart a distance of 1 m and then released. As they approach each other, what happens to the force between them?

Answer 2

it gets bigger

Question 3

Answer 3

decreasing acceleration.

Question 4

Two identical small charged spheres are a certain distance apart, and each initially experiences an electrostatic force of magnitude F due to the other. With time, charge gradually diminishes on both spheres. When each of the spheres has lost half its initial charge, the magnitude of the electrostatic force will be:

Answer 4

1/4 F.

Question 5

The force between two charges separated by a distance d is F. If the charges are pulled apart to a distance 3d, what is the force on each charge?

Answer 5

1/9 F

Question 6

If two-point charges exert a force of 1 N on each other when they are 3 cm apart, they will exert a force of 1/25 N when they are 15 cm apart.

Answer 6

True

Question 7

Two unequal point charges q1 and q2 are held in a place separated from each other. A point charge Q is placed somewhere between them at a point where it remains stationary when released. From this observation, we can conclude that q1 and q2 must either both be positive, or both be negative.

Answer 7

True

Question 8

Three-point charges lie at the vertices of an equilateral triangle as shown. All three charges have the same magnitude, but charges #1 and #2 are positive (+q) and charge #3 is negative (–q). The net electric force that charges #2 and #3 exert on charge #1 is in what direction?

Answer 8

the –y-direction.

Question 9

Three-point charges lie at the vertices of an equilateral triangle as shown. All three charges have the same magnitude but charge #1 is positive (+q) and charges #2 and #3 are negative (–q). The net electric force that charges #2 and #3 exert on charge #1 is in what direction?

Answer 9

the +x-direction

Question 10

What is the electric field strength at x = 0 m, y = 0 m produced by two electrons, one at x = 0.0001 m, y = 0 m and the other at x = -0.0001 m, y = 0 m? (use k is 9.0 × 109 N·m2/C2.)

Answer 10

0 N/C

Question 11

Four charged particles (two having a charge +Q and two having a charge -Q) are distributed as shown below. Each charge is equidistant from the origin. In which direction is the net electric field at the point P, which is on the y axis?

Answer 11

upwards, toward the left