Q: Which equation correctly expresses Gauss's Law for electric fields?

$$\oint \vec{E} \cdot d\vec{A} = \frac{q_{\text{enc}}}{\$$epsilon_0$$}$$

Q: A proton is released from rest in a Van de Graaff accelerating system. The proton initially is located where the electric potential is $$5.0\ \mathrm{MV}$$ and then moves to a region where the potential is zero. What is the final speed of the proton?

$$3.09 \times 10^7$\ \mathrm{m/s}$$

Question 1

Which of the following statements best describes the quantization of electric charge?

Accepted Answer

Electric charge only occurs in integer multiples of the charge of an electron.

Question 2

A soap bubble of radius $$R is $$placed in a uniform electric field of magnitude $$E. $$What is the electric flux through the surface of the soap bubble?

Accepted Answer

0

Question 3

Three capacitors are connected in series, with $$C_1$$ \u003e $$C_2$$ \u003e $$C_3. $$The capacitors are fully charged. Let $$U_1$$, $$U_2$$, and $$U_3$$ represent, respectively, the potential energy stored in $$C_1$$, $$C_2$$, and $$C_3. $$Which of the following statements is true?

Accepted Answer

$$U_1$$ \u003c $$U_2$$ \u003c $$U_3$$

Question 4

A positive charge moves with a constant velocity toward the top of the page and enters a region of a uniform magnetic field pointing to the top of the page. What is the direction of the magnetic force on the charge?

Accepted Answer

To the right of the page.

Question 5

Three equal resistors, each of resistance $$R$$, are connected in series. What is their equivalent resistance when combined in parallel?

Accepted Answer

$$R/3$$

Question 6

A wire carries a steady current of $$2.4\ \mathrm{A}. $$The straight section of the wire is $$0.75\ \mathrm{m}$$ long and lies along the $$x-$$axis within a uniform field $$\vec{B} = 1.67\ \mathrm{T} in $$the $$z-$$direction. What is the magnitude of the magnetic force on the section of wire?

Accepted Answer

$$3.0\ \mathrm{N}$$

Question 7

Which equation correctly expresses Gauss's Law for electric fields?

Accepted Answer

$$\oint \vec{E} \cdot d\vec{A} = \frac{q_{	ext{enc}}}{\$$epsilon_0$$}$$

Question 8

A non-conducting solid sphere of radius $$10.0\ \mathrm{cm}$$ has a uniform charge density. The magnitude of the electric field at $$20.0\ \mathrm{cm}$$ from the sphere's center is $$1.88 	imes 10^3$\ \mathrm{N/C}. $$What is the magnitude of the electric field inside the sphere at a distance of $$5.00\ \mathrm{cm}$$ from the sphere's center?

Accepted Answer

$$470\ \mathrm{N/C}$$

Question 9

Which of the following is the correct expression for the energy stored in a parallel-plate capacitor?

Accepted Answer

$$U = \frac{1}{2}CV^2$

Question 10

A proton is released from rest in a Van de Graaff accelerating system. The proton initially is located where the electric potential is $$5.0\ \mathrm{MV}$$ and then moves to a region where the potential is zero. What is the final speed of the proton?

Accepted Answer

$$3.09 	imes 10^7$\ \mathrm{m/s}$$

Question 11

Which of the following correctly describes the direction of the magnetic force on a moving positive charge in a uniform magnetic field?

Accepted Answer

It is always perpendicular to both the velocity and the magnetic field.

Question 12

A south pole of a freely-suspended bar magnet will point toward which direction of the Earth?

Accepted Answer

All points toward the magnetic north pole.

Question 13

Which of the following is the correct formula for the capacitance of a parallel-plate capacitor?

Accepted Answer

$$C = \$$epsilon_0$$ \frac{A}{d}$$

Question 14

If the charges on two balloons are both doubled and the distance between them is quadrupled, how would the repulsive force between them change?

Accepted Answer

It would be reduced to one-eighth.

Question 15

Which of the following is the correct expression for the magnetic force on a wire of length $$L$$ carrying current $$I in a $$uniform magnetic field $$B$$?

Accepted Answer

$$F = ILB \sin 	heta$$

Question 16

Which of the following is the correct formula for the equivalent capacitance $$C_{eq} of $$capacitors $$C_1$$, $$C_2$$, and $$C_3$$ connected in parallel?

Accepted Answer

$$C_{eq} = C_1$ + C_2$ + C_3$

Question 17

A $$2.0\ \mathrm{A}$$ current flows through a $$120\ \Omega$$ resistor. How many joules are used by the heater if it runs for $$30\ \mathrm{s}$$?

Accepted Answer

$$240$$

Question 18

Which of the following is the correct formula for the electric field $$E$$ created by a point charge $$q at a $$distance $$r$$?

Accepted Answer

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

Question 19

Which of the following is the correct formula for the potential difference $$V$$ across a resistor of resistance $$R$$ carrying current $$I$$?

Accepted Answer

$$V = IR$$

Question 20

Which of the following is the correct formula for the equivalent resistance $$R_{eq} of $$resistors $$R_1$$, $$R_2$$, and $$R_3$$ connected in parallel?

Accepted Answer

$$\frac{1}{R_{eq}} = \frac{1}{R_1$} + \frac{1}{R_2$} + \frac{1}{R_3$}$$

Electricity and Magnetism: Study Notes for Chapters 21–29

Study Guide - Practice Questions

Study Guide - Flashcards