Question 1

Consider the configuration of four point charges shown in the first image. Which principle allows you to determine the net electric field at the location of $$q_1$$ due to the other charges?

Accepted Answer

The principle of superposition

Question 2

A point charge $$Q$$ creates an electric field at a distance $$r in $$vacuum. Which of the following correctly expresses the magnitude of the electric field?

Accepted Answer

$$\frac{Q}{4\pi\$$epsilon_0$$ r^2$}$$

Question 3

Refer to the configuration in the seventh image (three charges, $$+Q$$, $$+2Q$$, $$+Q). If$$ $$r \gg d$$, what is the approximate electric field at the dot?

Accepted Answer

$$\frac{4Q}{4\pi\$$epsilon_0$$ r^2$}$$

Question 4

In the eighth image (rectangle of charges), what is the direction of the net electric field at point A?

Accepted Answer

Down and to the right

Question 5

Which statement about electric field lines is correct?

Accepted Answer

Electric field lines start on positive charges and end on negative charges.

Question 6

In the tenth image (field lines between a positive and a negative charge), where is the electric field strongest?

Accepted Answer

Where the field lines are closest together

Question 7

What is the linear charge density $$\lambda$$ for a rod of length $$L$$ carrying total charge $$Q$$?

Accepted Answer

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

Question 8

For an infinite line of charge with linear charge density $$\lambda$$, what is the magnitude of the electric field at a distance $$r$$ from the line?

Accepted Answer

$$\frac{1}{4\pi\$$epsilon_0$$} \frac{2|\lambda|}{r}$$

Question 9

A charged ring of radius $$R$$ carries total charge $$q. $$What is the electric field at a point on the axis of the ring, a distance $$z$$ from its center?

Accepted Answer

$$E = \frac{kqz}{(z^2$ + R^2$)^{3/2}$$}$

Question 10

What is the electric field just outside an infinite plane of charge with surface charge density $$\eta$$?

Accepted Answer

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

Question 11

In a parallel-plate capacitor, what is the direction of the electric field inside the plates?

Accepted Answer

From the positive plate to the negative plate

Question 12

Which of the following best describes the electric field inside an ideal parallel-plate capacitor?

Accepted Answer

Uniform in magnitude and direction

Question 13

A charged particle of charge $$q$$ and mass $$m is $$placed in a uniform electric field $$E. $$What is its acceleration?

Accepted Answer

$$a = \frac{qE}{m}$$

Question 14

A water molecule has a dipole moment $$p. $$When placed in a uniform electric field $$E$$, what is the maximum torque experienced by the molecule?

Accepted Answer

$$	au_{max} = pE$$

Question 15

Which of the following statements about electric dipoles in a non-uniform electric field is correct?

Accepted Answer

The dipole experiences a net force toward the region of stronger field.

Question 16

A thin rod of length $$L$$ and total charge $$Q$$ lies along the $$x-$$axis. What is the expression for the electric field at a point $$P on $$the perpendicular bisector of the rod, a distance $$d$$ from the rod?

Accepted Answer

$$E = \frac{2k\lambda \sin \$$theta_0$$}{d}$$

Question 17

Which of the following is true about the electric field at three points inside a parallel-plate capacitor (see image with points 1, 2, 3)?

Accepted Answer

$$E_1$$ = $$E_2$$ = $$E_3$$

Question 18

A dipole is placed in a uniform electric field. Which of the following is true?

Accepted Answer

The net force on the dipole is zero, but it experiences a torque.

Question 19

A charged ink drop of mass $$1.3 	imes 10$$^{-10}$$ kg and charge 1.5$$ 	imes $$10^{-13} C $$enters a region between deflecting plates with a uniform electric field of $$1.4 	imes 10^6$ N/C directed downward. If the drop enters with horizontal velocity v_x = 18$ m/s and the plates are L = 1.6$ cm long, what is the vertical deflection y$ of the drop at the far edge of the plates?

Accepted Answer

$$y = \frac{$$qEL^2$$}{2mv_x^2$}$$

Chapter 23: The Electric Field – Principles, Calculations, and Applications

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