Slide 7 / 45 Slide 8 / 45 6 The wire above has a current I flowing - - PDF document

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AP Physics 2

Magnetic Field

Multiple Choice www.njctl.org

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

• f the magnetic field at a point east of the wire?

A North B South C West D East

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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

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3 The wire above has a current being carried to the right and point P is a distance r away from the wire. What is the direction of the magnetic field at P? A Out of the page B Into the page C Left D Right

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

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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

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

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

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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

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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

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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

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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

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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

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13 A magnetic field is created by the two parallel currents flowing in

• pposite directions. At what point is the magnetic field the greatest

in magnitude? A B B C C D D E

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14 A magnetic field is created by the two parallel currents flowing in

• pposite directions. 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

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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 D Bottom of the page

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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

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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

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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 B

0?

A Bo B 2 Bo C 4 Bo D Bo/2

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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 2 Fo B 4 Fo C Fo D Fo/2

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20 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. What is the direction of the electric field between the charged plates? A Left B Right C Top of the page D Bottom of the page

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21 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. In what direction will the particle move between the charged plates? A Left B Right C Up D Down

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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. 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

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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

• f the electron in the field?

A mv/eB B eB/mv C me/vB D mB/ev

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24 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. What is the direction of the magnetic force acting on the wire? A Left B Right C Top of the page D Bottom of the page

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25 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. 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

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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. What is the magnitude of the magnetic force acting on the wire? A 15 N B 1.5 N C 0.15 N D 0.015 N

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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(μoI/2πr) toward the lower left hand corner B 2(μoI/2πr) toward the upper left hand corner C (μoI/2πr) toward the lower right hand corner D 2(μoI/2πr) toward the lower right hand corner

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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

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29 Both wires above are in parallel with equal currents flowing in

• pposite 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

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

• rbit of the complete circle?

A 0 J B 10-20 J C 10-26 J D 103 J

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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. 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 105 m/s C 106 m/s D 107 m/s

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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

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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

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34 An electron is travelling with a velocity v and charge e into a region between two charged plates. There is a magnetic force that

• pposes the electric force due to the electric field of magnitude E
• n the electron.

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

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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

• pposes the electric force due to the electric field of magnitude E
• n the electron. 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

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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

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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

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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

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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

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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

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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

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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

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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

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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