ap physics 2 magnetic field multiple...

© njctl.org AP Physics 2 Magnetism

AP Physics 2

Magnetic Field

Multiple Choice

1. A straight wire carries a current into the page. What is the direction of the magnetic field

at a point east of the wire?

a. North

b. South

c. West

d. East

2. Above there is a circular loop of wire that has a counterclockwise current running

through it. What is the direction of the magnetic field inside of the loop?

a. North

b. South

c. Into the page

d. Out of the page


Questions 3-4

The wire above has a current being carried to the right and point P is a distance r away from the

wire.

3. What is the direction of the magnetic field at P?

a. Out of the page

b. Into the page

c. Left

d. Right

4. By how much would the magnetic field change if the current was doubled and the

distance r was doubled?

a. Doubled

b. Halved

c. Quadrupled

d. No change

5. A wire carries current out of the page in a region of magnetic field directed north. What is

the direction of the magnetic force on the current due to the magnetic field?

a. North

b. South

c. West

d. East


Questions 6-7

The wire above has a current I flowing to the left of the page, a mass m, and a length L.

6. In what direction would a magnetic field have to be placed so that the magnetic force

could cancel out the gravitational force on the wire?

a. Up

b. Down

c. Out of the page

d. Into the page

7. If the magnitude of the magnetic field is B what must the magnitude of this field be to

cancel out the gravitational force on the wire?

a. mg/IL

b. m/IL

c. IL/mg

d. mgL/I

8. An electron enters a region of uniform magnetic field in the -Z direction. What is the

direction of the magnetic force on the electron due to the magnetic field?

a. +X direction

b. +Y direction

c. -X direction

d. -Y direction


9. A physics student sets up an experiment with a long wire carrying current in the +Y

direction and a small ball attached to a thread with a charge of -q. Assuming that the

student cannot observe or measure changes in tension in what way can the student

move the ball so that there will be an observable magnetic force acting on the ball?

a. +X direction

b. +Z direction

c. +Y Direction

d. –X direction

10. A horizontal wire is carrying current to the east and a proton is moving with a velocity v

to the west. What is the direction of the magnetic force acting on the proton due to the

current carrying wire?

a. North

b. South

c. West

d. East


11. A circular loop of wire carries current in a counterclockwise direction. The loop is placed

in a uniform magnetic field directed into the page. What is the effect of the magnetic

force on the loop due to the field?

a. Rotates with respect to its axis

b. Rotates with respect to its diameter

c. Contracts in size

d. Expands in size

12. Shown above are two identical bar magnets that are fixed in place with a proton moving

to the right about to enter the region between these two magnets. Which statement

below best describes what happens to the proton while travelling in between the

magnets?

a. It curves downward and strikes the bottom magnet

b. The proton continues to move to the right in a straight line

c. It curves upward and strikes the top magnet

d. The proton stops and moves to the left in a straight line


Questions 13-14

A magnetic field is created by the two parallel currents flowing in opposite directions.

13. At what point is the magnetic field the greatest in magnitude?

a. B

b. C

c. D

d. E

14. What is the direction of the net magnetic field at point B?

a. Left

b. Right

c. Top of the page

d. Bottom of the page

15. Two parallel wires carry current in opposite directions. What is the direction of the

magnetic force on the current going into the page due to the current going out of the

page?

a. Left

b. Right

c. Top of the page



16. An electron enters a uniform electric field perpendicular to the field lines. What must be

the direction of the magnetic field in order to cancel the electric force effect?

a. Left

b. Right

c. Into the page

d. Out of the page

17. An electron enters a uniform electric field perpendicular to the field lines. What is the

magnitude of the magnetic field if the electric effect completely canceled?

a. Ev

b. v/E

c. E/v

d. Zero

18. What is the magnitude of the magnetic field at point B produced by a current I if the

magnitude of the field at point A is B0?

a. B0

b. 2B0

c. 4B0

d. B0 /2


19. Two parallel wires carry currents I1 and I2 in the same direction and separated by a

distance d. The magnitude of the magnetic force between the wires is F0. What is the

force between the wires if each current is doubled and the separation is quadrupled?

a. 2F0

b. 4F0

c. F0

d. F0 /2

Questions 20-22

Shown above is a mass spectrometer with a positively charged particle placed in between two

charged plates. The magnetic field is uniform and directed out of the page.

20. What is the direction of the electric field between the charged plates?

a. Left

b. Right

c. Top of the page


21. In what direction will the particle move between the charged plates?

a. Left

b. Right

c. Up

d. Down

22. Assuming that the particle escapes the region between the charged plates and enters

the region with the uniform magnetic field, which statement below would best describe

the particle’s path in this magnetic field?

a. Semi-circular downward path

b. Semi-circular upward path

c. Parabolic downward path

d. Parabolic upward path


23. An electron with a mass m and a charge e enters a uniform magnetic field B at a velocity

v. What is the radius of the curvature of the electron in the field?

a. mv/eB

b. eB/mv

c. me/vB

d. mB/ev

Questions 24-26

Shown above is a magnet on the left placed onto an electronic balance that gives a reading of

100g. To the right the same magnet is placed on the electronic balance but a wire carrying

current into the page is placed directly in between the north and south ends of the magnet. To

the right the balance now reads 115 g.

24. What is the direction of the magnetic force acting on the wire?

a. Left

b. Right

c. Top of the page



25. What would happen if the current was increased in the wire?

a. The balance reading would decrease

b. The balance reading would increase

c. The balance reading would stay the same

d. The balance reading would increase for a few seconds and then go back to its

original reading

26. What is the magnitude of the magnetic force acting on the wire?

a. 15 N

b. 1.5 N

c. .15 N

d. .015 N

27. One wire is carrying current into the page and the other three wires are carrying current

out of the page. The distance between each wire and point A is r. What is the magnitude

and direction of the magnetic field at point A?

a. 2 (𝜇0𝐼/2𝜋𝑟) toward the lower left hand corner

b. 2 (𝜇0𝐼/2𝜋𝑟) toward the upper left hand corner

c. (𝜇0𝐼/2𝜋𝑟) toward the lower right hand corner

d. 2 (𝜇0𝐼/2𝜋𝑟) toward the lower right hand corner


28. Two wires are both carrying current up towards the top of the page. What is the

interaction between these two wires which results from the magnetic fields they create?

a. Attraction

b. Repulsion

c. Magnetic fields cancel out

d. None of the above

29. Both wires above are in parallel with equal currents flowing in opposite directions. At

what location would the magnetic fields cancel out?

a. Anywhere on the line xx’

b. Anywhere on the line yy’

c. Anywhere on the line Ax’

d. At no points on the diagram


Questions 30-31

A magnetic field of 1 T causes a proton beam of 2 mA to move in a circle with a radius of 0.1 m.

Assume that the magnetic field is perpendicular to the plane that the circle is located on.

30. What is the best estimate of the work done in Joules on the protons in each orbit of the

complete circle?

a. 0 J

b. 10 -20 J

c. 10 -26 J

d. 10 3 J

31. What is the best estimate of the speed of a single proton in this beam of protons moving

in a circle due to the magnetic field?

a. 10 -3 m/s

b. 10 5 m/s

c. 10 6 m/s

d. 10 7 m/s

32. Shown above there is an electron moving to the right undeflected by both the electric

field in between the plates and the magnetic field coming out of the page in between the

plates. The magnetic field has a magnitude of 2.0 T and the electric field has a

magnitude of 8 N/C. What is the speed of the electron?

a. 0.25 m/s

b. 2 m/s

c. 4 m/s

d. 0.5 m/s

33. A particle with a negative charge has an initial velocity that is parallel to a magnetic field

moving to the right. What path would this negatively charged particle follow?

a. Parabolic arc

b. Spiral

c. Circular arc

d. Straight line parallel to the field


Questions 34-35

An electron is travelling with a velocity v and charge e into a region between two charged plates.

There is a magnetic force that opposes the electric force due to the electric field of magnitude E

on the electron.

34. What direction would the magnetic field have to be in?

a. Directed into the page

b. Directed out of the page

c. Toward the top of the page

d. Toward the bottom of the page

35. What would the magnitude of the magnetic field be for the electron to pass through the

region between the plates undeflected?

a. v/E

b. E/v

c. e/v

d. E/ve


36. A positively charged particle in a uniform magnetic field B moves with a constant speed

v and has a charge of e. The particle moves in a circle of radius r. Which of the following

graphs plotting radius versus magnetic field best represents the described situation?

a.

b.

c.

d.


37. When a magnetic field is applied to this type of material, its magnetic domains line up

opposite the applied magnetic field and it is repelled. What type of material is this?

a. Paramagnetic

b. Ferromagnetic

c. Diamagnetic

d. Anti-magnetic

38. The magnetic moment of an electron:

a. points in the direction of the north pole created by the electron

orbit and increases with the strength of the magnetic field.

b. points in the direction of the north pole created by the electron

orbit and decreases with the strength of the magnetic field

c. points in the direction of the south pole created by the electron

orbit and decreases with the strength of the magnetic field

d. points in the direction of the south pole created by the electron

orbit and decreases with the strength of the magnetic field.

39. Magnetic field lines:

a. leave the south pole and enter the north pole of a magnet.

b. leave the north pole and enter the south pole of a magnet.

c. leave the south pole of a magnet and enter the south pole of

another magnet.

d. leave the north pole of a magnet and enter the north pole of

another magnet.

40. If a charged particle enters an external magnetic field and it moves in a circular orbit,

what must be true?

a. The particle maintains a constant velocity in the field.

b. The particle maintains a constant speed in the field.

c. Positive work is done by the field on the particle.

d. Negative work is done by the field on the particle.


41. A physics student decided to fix three magnets in place and place iron filings around the

magnets to view the magnetic field lines created. An image of what the student saw is

shown above. According to this image what poles would have to be the same kind as

pole E to produce the result shown above? Select two answers.

a. A

b. B

c. C

d. D

42. There is a square desk viewed from above with a particle of charge -e at rest on the

desk. Both an electric field and a magnetic field are directed out of the table. Which

statement below is true? Select two answers.

a. FE is directed into the table

b. FB is directed into the table

c. FB > FE

d. FE > FB


43. A charged particle enters a uniform magnetic field with velocity v that is perpendicular to

the magnetic field. Which of the following can be a possible path of the charged particle?

Select two answers.

a. D

b. E

c. F

d. G

44. Assume that both magnets shown above are far enough away that their forces do not

affect each other. If each magnet shown was cut along the dotted line then which

statements below are true? Select two answers.

a. The top pair of magnets would experience repulsion

b. The bottom pair of magnets would experience repulsion

c. The top pair of magnets would experience attraction

d. The bottom pair of magnets would experience attraction


Answers

1. b

2. d

3. a

4. d

5. c

6. c

7. a

8. a

9. b

10. a

11. c

12. b

13. d

14. d

15. b

16. d

17. c

18. b

19. c

20. b

21. b

22. a

23. a

24. d

25. b

26. c

27. a

28. a

29. d

30. a

31. d

32. c

33. d

34. a

35. b

36. a

37. c

38. a

39. b

40. b

41. b, d

42. a, d

43. c, d

44. a, d

ap physics 2 magnetic field multiple...

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