Question

1. The electric potential two meters above the ground is measured to be -5V. What is the electric field at this point?

Select one:

a. 2.5 N/C and pointing upward

b. 2.5 N/C and pointing downward

c. 10 N/C and pointing downward

d. You cannot tell from the information given.

e. 10 N/C and pointing upward

2. As a charged particle moves a distance of 2 meters, the electric potential increases uniformly by 5V. What is the magnitude of the electric field over that region?

Select one:

a. 5 N / C

b. It depends on the charge of the particle.

c. 10 N/ C

d. 2.5 N / C

e. 0.4 N / C

3. An electric potential increases by 4 volts for every 0.5 meters above the top of a table. What is the electric field strength directed along the surface of the table?

Select one:

a. You cannot tell from the information given.

b. 2 N/C

c. 0.5 N/C

d. 8 N/C

e. 0 N/C

4. What are the units of electric potential?

Select one:

a. Joules

b. Farads

c. Newtons / Coulombs

d. Volts

e. Coulombs

5. What types of quantities are electric field and electric potential?

Select one:

a. Both are scalars.

b. Both are vectors.

c. Electric field is a vector. Electric Potential is a scalar.

d. Electric field is a scalar. Electric Potential is a vector.

6. What can you say about the shape of electric field lines and equipotential surfaces?

Select one:

a. Electric field lines are parallel to equipotential surfaces for positive charges and perpendicular to equipotential surfaces for negative charges.

b. Electric field lines closely match the shape of equipotential surfaces.

c. Electric field lines are always parallel to equipotential surfaces.

d. The shape of electric field lines and equipotential surfaces are not closely related.

e. Electric field lines are always perpendicular to equipotential surfaces.

7. As a charged particle moves a distance of 2 meters, the electric potential increases uniformly by 5V. What is the change in electric potential energy of the particle?

Select one:

a. 0.4 J

b. 10 J

c. It depends on the charge of the particle.

d. 2.5 J

e. 5 J

8. An electric field points from the left side of your computer screen towards the right side. On which side of your screen is the electric potential higher?

Select one:

a. The potential is constant everywhere

b. The potential is higher on the left side.

c. Cannot tell from the information given.

d. The potential is higher on the right side.

9. Positive charges experience forces in what directions? Select all answers that are correct for full credit.

Select one or more:

a. In the direction of decreasing electric potential.

b. In the same direction as electric fields

c. Along equipotential surfaces

d. In the direction of increasing electric potential.

e. In opposite the direction of electric fields

10. A positive charge moves through a region of space where the electric potential decreases. How does the speed of the charge change?

Select one:

a. The speed increases.

b. The speed decreases.

c. The speed does not change.

d. There is not enough information to tell if the speed will change.

e. The speed will change, but if it increases or decreases depends on the mass of the particle.

Answer 1

1. Potential is decreasing as we go above the surface of earth, which is considered to have zero potential. A positive test charge always goes to decreasing potential, that is the direction of electric field. So the Magnitude of this field is

5 - 0/2 = 2.5N/C

And the direction is upward. a. 2.5 N/C and pointing upward is the correct option

2. With the same argument as in 1, the field is same, 2.5N; but as the charge of the particle is not mentioned so the direction is inconclusive. d. 2.5 N / C is the correct option.

3. d. 8 N/C is the correct option because field strength = change in potential / distance = 4/0.5 = 8N/C

4. c. Newtons / Coulombs is the correct option.

5. c. Electric field is a vector. Electric Potential is a scalar

6. e. Electric field lines are always perpendicular to equipotential surfaces.

7. potential energy = potential*charge of the particle ,so c. It depends on the charge of the particle is correct.

8. b. The potential is higher on the left side. is the correct option (see question 1)

9. a. In the direction of decreasing electric potential.
b. In the same direction as electric fields are the correct options.

10. The force on the particle is determined by the field strength on that point, and this force decides what the speed of the particle is going to be. As field strength entirely depends on the distribution of field lines.

Imagine a positive charge and a positive test charge near it, as the test charge is set free it will be repelled with a great force and will have high speed. Now as it goes further the force and the potential both decreases, so the speed is decreasing.

Do the same, but with a negative charge at the center, potential decreases as the test charge comes closer to the negative charge, but the force increases so the speed is now increasing with decreasing potential.

For parallel field lines this test charge will gain speed as it goes to a lower potential.

So, as the field line distribution is unknown d. There is not enough information to tell if the speed will change. is the correct option.