Physics Magnetism Exam 3

Which of the following cannot induce a voltage in a loop of wire? A. Moving a magnet near the loop. B. Moving the loop near a magnet. C. Expanding or contracting the loop in a region where there is no magnetic field. D. Changing the current in a nearby loop.

C

A cross section of the magnetic field for a current-carrying wire is shown. The direction of the current is A) to the left. B) to the right

A

A magnet on a frictionless mount would have its magnetic north pole point toward the Earth's geographic A) south pole B) north pole

A

If a current of negative charge flows in a circle in the direction of one's curled fingers of the right hand, the resulting magnetic field would be in the direction A. of the right index finger. B. of the thumb of the right hand. C. opposite to the thumb of the right hand. D. of due north.

C

A magnetic compass points towards the north geographic pole of the Earth because A. all magnetic poles, north or south, point that way due to the spin of the Earth. B. the static electricity in the atmosphere causes the alignment of the compass. C. there is a north magnetic pole near the north geographic pole. D. there is a south magnetic pole near the north geographic pole.

D

Two wires, each carrying current I, are antiparallel to each other. The two wires A) repel each other. B) attract each other. C) are not affected by each other

A

When a switch is closed allowing current to flow in coil A, the current induced in a nearby coaxial but unconnected coil B will flow A. only momentarily and then stop B. steadily until the current flow in A is shutoff C. will not flow at all since the coils are not connected D. will keep flowing long after the current in A is shut off

A

You could use two parallel wires to move objects 1 and 2 apart if each wire is embedded in its own object and if A. the currents in the wires are in opposite directions. B. the currents in the wires are in the same direction. C. one wire carries a current and the other wire has zero current.

A

A transformer has 200 turns on the primary and 20 turns on the secondary. The primary is connected to a direct current source of 100 millivolts. The voltage in the secondary coil will be A. zero. B. 10 millivolts. C. 20 millivolts. D. 1000 millivolts. E. 4000 millivolts.

B

A transformer is to be used to step down voltage from an alternating current source from 220 V to 110 V. If the primary has 120 turns, then the number of turns in the secondary is A. 2. B. 60. C. 240. D. 720. E. 1320.

B

If an electron is placed at rest near a bar magnet, the electron will A. accelerate away from the negative pole of the magnet. B. not move at all. C. be attracted to the positive pole of the magnet. D. move in a circular path around the north pole of the magnet.

B

. Electrons flow around a circular wire loop in a horizontal plane, in a direction that is clockwise when viewed from above. This causes a magnetic field. Inside the loop, the direction of this field is A. toward the center of the loop. B. radially outward from the center of the loop. C. up, toward the viewer. D. down, away from the viewer.

C

If an electron moves in a magnetic field, A. it always feels a force. B. it only feels a force if its velocity vector is parallel (or antiparallel) to the direction of the magnetic field. C. it only feels a force if its velocity vector is not parallel (or antiparallel) to the direction of the magnetic field. D. it does not feel a force if it is in motion, only if stationary.

C

A current flowing through a long, straight wire causes a magnetic field that points A. along the wire. B. along concentric circles around the wire. C. radially inward toward the wire. D. radially outward from the wire.

B

A horizontally moving positive sodium ion enters a magnetic field that points up. The magnetic force pushes the charge out of its original path. When viewed as shown on this page, what direction will the magnetic force point? A. Into the page B. Out of the page C. There is not enough information to answer.

B

A long straight wire carries a current. A positive charge moves toward the wire in a direction perpendicular to the wire. The direction of the force on the charge will be A. parallel to the wire in the direction of the current. B. parallel to the wire opposite the direction of the current. C. in the direction of the charge's velocity. D. opposite the direction of the charge's velocity. E. There is no force.

B

The magnetic field lines of a bar magnet A) emerge from the north pole and go back into the north pole B) emerge from the north pole and go into the south pole C) emerge from the south pole and go back into the south pole D) emerge from the south pole and go into the north pole

B

The magnetic field lines produced by a current in a straight wire A) are directed outward in a direction perpendicular to the wire B) are directed in concentric circles around the wire C) begin on one side of the wire and end on the other side of the wire

B

The magnetic pole near the Earth's north geographic pole actually has to be A. an N pole because it repels the S pole of your compass needle. B. an S pole, because it attracts the N pole of your compass needle. C. either an N or an S pole, but scientists have not determined which one yet.

B

In the southern hemisphere, the north pole of a compass needle A. points toward the south geographic pole because there is a south magnetic pole there. B. points toward the south geographic pole because that is the nearest magnetic pole. C. points away from the south geographic pole because there is a north magnetic pole there. D. spins aimlessly because the north geographic pole is beyond the horizon.

C

Magnetic fields affect A. neither electric charges in motion nor electric charges at rest. B. both electric charges in motion and electric charges at rest. C. only electric charges in motion. D. only electric charges at rest.

C

You see a positively charged helium ion in space, and it is at rest with respect to your spacecraft. Since you are studying for the final exam, you decide to experiment. You slowly push the N pole of a bar magnet closer to the helium ion. What happens to the helium ion? A. It experiences a magnetic force and moves off. B. It depends on whether it is a positive ion or a negative ion. C. Nothing happens, because the ion is not moving.

C

Imagine a magnetic field pointing into the plane of this page. An electron moves across the paper from left to right. The direction of the magnetic force on the electron will be A. into the plane of the paper. B. out of the plane of the paper. C. in the plane of the paper and toward the top of the page. D. in the plane of the paper and toward the bottom of the page. E. in the plane of the paper and opposite the electron's velocity

D

A horizontal straight wire carries a current from east to west. The resulting magnetic field lines are A. straight lines perpendicular to the wire. B. parallel to the wire from west to east. C. parallel to the wire from east to west. D. closed circles perpendicular to the wire directed counterclockwise as viewed from the east. E. closed circles perpendicular to the wire directed clockwise as viewed from the east.

E

A loop of wire is oriented in the magnetic field as shown below (the plane of the loop is perpendicular to the direction of the magnetic field). Which of the following is true? A. There will be an induced current only if the loop is moved to the left. B. There will be an induced current only if the loop is moved to the right. C. There will be an induced current only if the loop is moved upward. D. There will be an induced current only if the loop is moved downward. E. There will be an induced current if the loop is moved either up or down.

E

Imagine that this classroom contains a constant magnetic field that points from the front to the back. In front of you a negative charge is slowly moving horizontally to your left. As you watch, the magnetic force on the charge A. is away from you. B. is vertically down. C. is toward you. D. is horizontally to the right. E. is vertically up.

E