Physics II Exam 3 Conceptual
A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Fig. 27-6. If there is a current I flowing through this coil, what is the force acting on section BC of this coil?
0 N
Three particles travel through a region of space where the magnetic field is out of the page, as shown in Fig. 27-4. The electric charge of each of the three particles is, respectively,
1 is negative, 2 is neutral, and 3 is positive.
The maximum torque on a current carrying loop occurs when the angle between the loop's magnetic moment and the magnetic field vector is
90
If the south pole of one bar magnet is brought near the north pole of a second bar magnet, the two magnets will
Attract
A horizontal, long current-carrying wire is hanging from a vertical thread. The current is oriented into the plane of Fig. 27-2 shown above. A uniform magnetic field is applied and the wire is pulled away from the vertical. Which of the arrows labeled A to D correctly indicate the direction of the magnetic field? FIGURE 27-2 A horizontal, long current-carrying wire is hanging from a vertical thread. The current is oriented into the plane of Fig. 27-2 shown above. A uniform magnetic field is applied and the wire is pulled away from the vertical. Which of the arrows labeled A to D correctly indicate the direction of the magnetic field? ABCDThe magnetic field is oriented into the plane of the picture.
C
A constant magnetic flux can be used to produce an electric current.
False
A wire of length L carrying a current I is placed in a magnetic field. The direction of the magnetic field is opposite the direction of the current. In this situation, the wire experiences a maximum force.
False
Cutting a bar magnet near its north end results in a smaller mostly north pole magnet and a larger mostly south pole magnet.
False
If two identical wires carrying a certain current in the same direction are placed parallel to each other, they will experience a force of repulsion.
False
The field near a long straight wire carrying a current is inversely proportional to the current flowing through the wire.
False
The magnetic field near a current carrying wire is directly proportional to the distance from the wire.
False
The magnitude of the magnetic field inside a solenoid is inversely proportional to the current flowing through the solenoid.
False
In the figure, charged particles move in the vicinity of a current-carrying wire. For each charged particle, the arrow indicates the direction of motion of the particle, and the + or - indicates the sign of the charge. For each of the particles, indicate the direction of the magnetic force due to the magnetic field produced by the wire.(Figure 1) The upper left positive particle
Force is downward
In the figure, charged particles move in the vicinity of a current-carrying wire. For each charged particle, the arrow indicates the direction of motion of the particle, and the + or - indicates the sign of the charge. For each of the particles, indicate the direction of the magnetic force due to the magnetic field produced by the wire.(Figure 1) The upper right negative particle
Force is to the left
In the figure, charged particles move in the vicinity of a current-carrying wire. For each charged particle, the arrow indicates the direction of motion of the particle, and the + or - indicates the sign of the charge. For each of the particles, indicate the direction of the magnetic force due to the magnetic field produced by the wire.(Figure 1)The lower right positive particle
Force is to the left
In the figure, charged particles move in the vicinity of a current-carrying wire. For each charged particle, the arrow indicates the direction of motion of the particle, and the + or - indicates the sign of the charge. For each of the particles, indicate the direction of the magnetic force due to the magnetic field produced by the wire.(Figure 1) The lower left negative particle
Force is upward
In the relation F→=Iℓ→×B→F→=Iℓ→×B→, which pairs of the vectors (F→,ℓ→,B→)(F→,ℓ→,B→) are always at 90∘∘ ?
F→F→ and ℓ→ℓ→F→F→ and B→B→
A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Figure 27-6. If there is a current I flowing through this coil, what is the force acting on section AB of this coil?
ILB
Suppose you are holding a circular ring of wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. In each case, if your answer is yes, specify the direction. Is a current induced when the magnet is held steady within the ring?
No, there is no current induced.
If the north poles of two bar magnets are brought close to each other, the magnets will
Repel
If the number of turns on the secondary coil of a transformer are less than those on the primary, the result is a
Stepdown transformer
A beam of electrons is directed toward a horizontal wire carrying a current from left to right (see the figure).(Figure 1) In what direction is the beam deflected?
The beam is deflected to the right.
A horseshoe magnet is held vertically with the north pole on the left and south pole on the right. A wire passing between the poles, equidistant from them, carries a current directly away from you.
The force is directed downward
Which of the following statements is correct? Earth's geographic north pole is the north pole of the Earth's magnetic field. The north pole of a magnet points towards the Earth's geographic south pole. The north pole of a magnet points towards the Earth's geographic north pole.Earth's geographic south pole is the south pole of the Earth's magnetic field. None of the above statements is correct..
The north pole of a magnet points towards the Earth's geographic north pole.
A horizontal rod (oriented in the east-west direction) is moved northward at constant velocity through a magnetic field that points straight down. Make a statement concerning the potential induced across the rod.
The west end of the rod is at higher potential than the east end.
A changing magnetic flux through a closed loop of wire induces an emf in that loop.
True
A charged particle traveling opposite to a magnetic field does not experience a magnetic force.
True
A current carrying wire placed in a magnetic field perpendicular to the wire experiences a maximum force.
True
Magnetic field lines can never cross one another.
True
The emf in a conducting rod of length L moving perpendicular to a magnetic field is directly proportional to the speed of the rod.
True
The magnetic field unlike the electric field is continuous.
True
The negative sign in the Faraday's equation for electromagnetic induction is related to the direction of the induced emf.
True
Which of the following is correct? When a current carrying wire is in your right hand, thumb in the direction of the magnetic field lines, your fingers point in the direction of the current. When a current carrying wire is in your left hand, thumb in the direction of the magnetic field lines, your fingers point in the direction of the current. When a current carrying wire is in your right hand, thumb in the direction of the magnetic field lines, your fingers point in the direction of the magnetic field lines. When a current carrying wire is in your left hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines. When a current carrying wire is in your right hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
When a current carrying wire is in your right hand, thumb in the direction of the current, your fingers point in the direction of the magnetic field lines.
A charged particle moves in a straight line through a particular region of space. Could there be a nonzero magnetic field in this region?
Yes
Suppose you are holding a circular ring of wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. In each case, if your answer is yes, specify the direction. Is a current induced in the wire?
Yes, the current is induced clockwise.
Suppose you are holding a circular ring of wire and suddenly thrust a magnet, south pole first, away from you toward the center of the circle. In each case, if your answer is yes, specify the direction. Is a current induced when you withdraw the magnet?
Yes, the current is induced counterclockwise.
As a coil is removed from a magnetic field an emf is induced in the coil causing a current to flow within the coil. This current interacts with the magnetic field producing a force which
acts in the direction opposite to the coil's motion.
Magnetic flux depends upon the magnetic field. the area involved. the orientation of the area with respect to the field all of the above none of the above
all of the above
An electron moving along the +x-axis enters a magnetic field. If the electron experiences a magnetic deflection in the -y direction, what is the direction of the magnetic field in this region?
along the -z-axis
In using Ampere's law, the integral must be evaluated
around a closed path.
A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current
circles the wire in a counter-clockwise direction.
A circular loop of wire of area 25 cm2 lies in the plane of the paper. An increasing magnetic field B is coming out of the paper. What is the direction of the induced current in the loop?
clockwise
A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held with its south pole downward, vertically above the center of the coil. The magnet is released from rest and falls toward the coil. As viewed from above, you can say that, as it falls, the magnet induces
clockwise current in the loop.
A 200-loop coil of cross sectional area 8.5 cm2 lies in the plane of the paper. Directed out of the plane of the paper is a magnetic field of 0.06 T. The field out of the paper decreases to 0.02 T in 12 milliseconds. What is the direction of the current induced?
counterclockwise
A long straight wire lies on a horizontal table and carries an ever-increasing current northward. Two coils of wire lie flat on the table, one on either side of the wire. When viewed from above, the induced current circles
counterclockwise in the east coil and clockwise in the west coil.
A long, straight wire carrying a current is placed along the y-axis. If the direction of the current is in the +y direction, what is the direction of the magnetic field due to this wire?
counterclockwise, around the y-axis
A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle's weight, the particle will
follow a circular path.
A transformer is a device used to
increase or decrease an ac voltage.
A square loop of wire carrying a current in a clockwise direction lies in the plane of the paper. The magnetic field inside the loop is directed
into the paper everywhere.
Two parallel wires carry currents in the same direction. The direction of the force on one wire
is toward the other wire.
Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at the point exactly between the two wires
is zero.
An electric generator converts
mechanical energy into electrical energy
A circular coil of copper wire is lying flat on a horizontal table. A bar magnet is held with its south pole downward, vertically above the center of the coil. The magnet is kept stationary with respect to the coil. As viewed from above, you can say that the magnet induces
no current in the loop.
A rectangular coil, with corners labeled ABCD, of length L and width w is placed in a magnetic field B as shown in Figure 27-6. If there is a current I flowing through this coil, what is the direction of the force acting on section AB of this coil?
perpendicular to and into the page
The direction of the force on a current-carrying wire in a magnetic field is described by
perpendicular to both the current and the magnetic field
A proton is moving at an angle of 80° to a uniform magnetic field. What is the relationship between the direction of the force on the proton and the direction of the magnetic field?
perpendicular to the magnetic field
Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current toward you, and the wire on your left carries current away from you. From your point of view, the magnetic field at the point exactly midway between the two wires
points down.
A current carrying circular loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, inside the loop? The magnetic field
points straight up.
The magnetic field produced by a long straight current-carrying wire is
proportional to the current in the wire and inversely proportional to the distance from the wire.
A vertical wire carries a current straight down. To the east of this wire, the magnetic field points
south
The force on a current-carrying wire in a magnetic field is equal to zero when
the current is parallel to the field lines.
The force on a current-carrying wire in a magnetic field is the strongest when
the current is perpendicular to the field lines.
The earth's northern magnetic pole acts like
the south pole of a magnet.
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the same direction,
the wires attract each other.
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions,
the wires repel each other
Electric power is transmitted over long distances at high voltage because
there is less power lost
A proton, moving east, enters a magnetic field of a certain strength. Because of this field the proton curves downward. What is the direction of the magnetic field?
towards the south
A proton, moving west, enters a magnetic field of a certain strength. Because of this magnetic field the proton curves upward. What is the direction of this magnetic field?
towards the south
An electron, moving south, enters a magnetic field of certain strength. Because of this field the electron curves upward. What is the direction of the magnetic field?
towards the west
A vertical wire carries a current straight up in a region where the magnetic field vector points due north. What is the direction of the resulting force on this current?
west
Which can be at other angles?
ℓ→ℓ→ and B→B→