Question 1

Which of the following best describes the direction of the electric field produced by a positive point charge at a point in space?

Accepted Answer

The electric field points directly away from the charge.

Question 2

A test charge $$q_0 is $$placed at a distance $$r$$ from a point charge $$q. $$What is the magnitude of the electric field at that point?

Accepted Answer

$$E = \frac{1}{4\pi\$$varepsilon_0$$} \frac{|q|}{r^2$}$$

Question 3

If the electric field at a point due to a charge $$q is$$ $$\vec{E}$$, what is the force experienced by a test charge $$q_0$$ placed at that point?

Accepted Answer

$$\vec{F} = q_0$ \vec{E}$$

Question 4

Which of the following statements about the electric field of a negative point charge is correct?

Accepted Answer

The electric field points toward the charge.

Question 5

Two identical positive point charges are placed symmetrically on the x-axis at $$x = +d/2$$ and $$x = -d/2. $$What is the direction of the net electric field at a point $$P$$ located on the z-axis above the origin?

Accepted Answer

The net electric field points in the positive z-direction.

Question 6

Which equation correctly gives the electric field at a distance $$z$$ above the midpoint between two equal charges separated by distance $$d ($$where $$d \ll z$$)?

Accepted Answer

$$\vec{E}(z) = \frac{1}{4\pi\$$varepsilon_0$$} \frac{qd}{z^3$} \hat{i}$$

Question 7

A proton is placed in a uniform electric field pointing upward. What is the direction of the force on the proton?

Accepted Answer

Upward, in the same direction as the electric field.

Question 8

Which of the following best explains why the horizontal components of the electric field from two identical charges placed symmetrically about the z-axis cancel at a point on the z-axis?

Accepted Answer

The horizontal components are equal in magnitude but opposite in direction.

Question 9

A small negative test charge is placed near a large positive charge. What is the direction of the force on the test charge?

Accepted Answer

Toward the positive charge.

Question 10

Which of the following is the correct expression for the electric field at a distance $$r$$ from a point charge $$q in $$vacuum?

Accepted Answer

$$\vec{E} = \frac{1}{4\pi\$$varepsilon_0$$} \frac{q}{r^2$} \hat{r}$$

Question 11

A charged dust particle in the air experiences a downward gravitational force and an upward electric force. If the particle remains stationary, what is the relationship between the electric field $$E$$ and the charge $$q of $$the particle?

Accepted Answer

$$qE = mg$$

Question 12

Which of the following statements is true about the superposition principle for electric fields?

Accepted Answer

The net electric field at a point is the vector sum of the electric fields produced by each charge individually.

Question 13

A point charge $$q is $$placed at the origin. At which location is the electric field due to this charge the strongest?

Accepted Answer

At the point closest to the origin.

Question 14

If the distance between two point charges is doubled, how does the magnitude of the electric field at a point due to one of the charges change?

Accepted Answer

It becomes one-fourth as large.

Question 15

Which of the following is a correct analogy between electric and gravitational fields?

Accepted Answer

Electric field is to charge as gravitational field is to mass.

Question 16

A hospital uses an electrostatic precipitator to remove dust from the air. If the dust particles are negatively charged, in which direction should the electric field be applied to move the dust toward a collecting plate at the top of the device?

Accepted Answer

The electric field should point downward.

Question 17

A student claims that the electric field at the midpoint between two equal and opposite charges is zero. Is this correct?

Accepted Answer

Yes, because the fields from each charge are equal in magnitude and opposite in direction.

Question 18

Which of the following best describes the electric field lines around a single negative point charge?

Accepted Answer

They radiate inward toward the charge.

Question 19

A charged balloon sticks to a wall after being rubbed on hair. Which of the following best explains this phenomenon in terms of electric fields?

Accepted Answer

The electric field from the balloon induces opposite charges on the wall, resulting in an attractive force.

Electric Field: Concepts, Formulas, and Applications (General Physics II, Chapter 5.4)

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