Question 1

Which of the following correctly describes the direction of electric field lines around a positive point charge?

Accepted Answer

Electric field lines point radially outward from the charge.

Question 2

What is the magnitude of the electric field at a distance $$r$$ from a point charge $$q in $$vacuum?

Accepted Answer

$$E = \frac{q}{4\pi\$$epsilon_0$$ r^2$}$$

Question 3

A thin, infinitely long wire has a uniform linear charge density $$\lambda. $$What is the electric field at a distance $$r$$ from the wire?

Accepted Answer

$$E = \frac{\lambda}{2\pi\$$epsilon_0$$ r}$$

Question 4

Which principle allows you to calculate the net electric field at a point due to multiple charges?

Accepted Answer

Principle of superposition

Question 5

A water molecule is a permanent dipole. What is the direction of the electric field at a point on the axis of the dipole, far from the molecule?

Accepted Answer

The field points away from the positive end of the dipole.

Question 6

What is the electric field at a distance $$z$$ along the axis from the center of a ring of radius $$R$$ carrying total charge $$Q$$?

Accepted Answer

$$E = \frac{Qz}{4\pi\$$epsilon_0$$ (z^2$ + R^2$)^{3/2}$$}$

Question 7

A parallel plate capacitor has plates with charge $$+Q$$ and $$-Q. $$What is the electric field between the plates (ignoring edge effects)?

Accepted Answer

$$E = \frac{Q}{\$$epsilon_0$$ A}$$

Question 8

Which of the following statements about electric field lines is FALSE?

Accepted Answer

Electric field lines can cross each other.

Question 9

A flat circular ring of radius $$R$$ carries a total charge $$Q$$ uniformly distributed. What is the surface charge density $$\sigma$$?

Accepted Answer

$$\sigma = \frac{Q}{2\pi R^2$}$$

Question 10

Two protons, A and B, are in a uniform electric field. Proton A is twice as massive as proton B. Which proton has the larger acceleration?

Accepted Answer

Proton B

Question 11

What is the SI unit of the electric field?

Accepted Answer

Newton per Coulomb (N/C)

Question 12

A thin rod of length $$L$$ carries a total charge $$Q$$ uniformly distributed. What is the linear charge density $$\lambda$$?

Accepted Answer

$$\lambda = \frac{Q}{L}$$

Question 13

Which equation gives the electric field at a point on the bisecting plane of a dipole at distance $$r$$ from the center?

Accepted Answer

$$E_{dipole} = -\frac{1}{4\pi\$$epsilon_0$$} \frac{p}{r^3$}$$

Question 14

A sphere of charge $$Q$$ and radius $$R$$ produces an electric field outside the sphere that is:

Accepted Answer

Identical to the field of a point charge $$Q at $$the center.

Question 15

What is the $$y-$$component of the electric field at the dot due to the shaded region of charge on a rod of length $$L$$ and total charge $$Q$$?

Accepted Answer

$$\frac{Q}{L} \frac{y}{4\pi\$$epsilon_0$$ (x^2$ + y^2$)} dx$$

Question 16

Which of the following best describes the electric field inside a uniformly charged spherical shell?

Accepted Answer

The field is zero everywhere inside the shell.

Question 17

A dipole is placed in a uniform electric field. What happens to the dipole?

Accepted Answer

It experiences a torque but no net force.

Question 18

Which of the following is the correct expression for the electric field at a distance $$r$$ from an infinite plane of charge with surface charge density $$\eta$$?

Accepted Answer

$$E = \frac{\eta}{2\$$epsilon_0$$}$$

Question 19

An electron is placed in the plane that bisects a dipole. What is the direction of the electric force on the electron?

Accepted Answer

Away from the dipole along the bisecting plane.

Electric Fields: Point Charges, Dipoles, Continuous Distributions, and Field Lines

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