Question 1

Two solenoids are close to each other,as shown in the figure,with the switch S open.When the switch is suddenly closed,which way will the induced current flow through the galvanometer in the left-hand solenoid? 
A)from left to right
B)from right to left
C)There will be no induced current through the galvanometer.

Accepted Answer

B

Question 2

An outer metal ring surrounds an inner metal ring,as shown in the figure.The current in the outer ring is counterclockwise and decreasing.What is the direction of the induced current in the inner ring? 
A)clockwise
B)counterclockwise
C)There is no induced current in the inner ring.

Accepted Answer

B

Question 3

A coil of wire containing N turns is in an external $\vec { B }$ field that is perpendicular to the plane of the coil and it steadily changing in magnitude.Under these circumstances,an emf ε is induced in the coil.If the rate of change of the magnitude of the $\vec { B }$ field and the number of turns in the coil are now doubled (but nothing else changes),what will be the induced emf in the coil?
A)2ε
B)ε/2
C)4ε
D)ε/4
E)ε

Accepted Answer

According to Faraday's law, the induced emf is given by ε = -N(dΦ/dt), where Φ is the magnetic flux through the coil. Doubling the magnitude of the external magnetic field and the number of turns in the coil will result in a fourfold increase in the magnetic flux through the coil. Therefore, the induced emf will be 4ε.

Question 4

A flat coil is in a uniform magnetic field.The magnetic flux through the coil is greatest when the plane of its area is
A)parallel to the magnetic field.
B)at 45° with the magnetic field.
C)perpendicular to the magnetic field.

Accepted Answer

When the plane of the coil is perpendicular to the magnetic field, the maximum number of magnetic field lines pass through the coil, leading to the maximum magnetic flux. This is because the magnetic field lines are effectively intersecting with the entire area of the coil. When the coil is parallel or at an angle with the magnetic field, only a fraction of the magnetic field lines intersect with the coil, decreasing the magnetic flux.

Question 5

A coil lies flat on a tabletop in a region where the $\vec { B }$ field vector points straight up.The magnetic field vanishes suddenly.When viewed from above,what is the sense of the induced current in this coil as the field fades?
A)The induced current flows counterclockwise.
B)The induced current flows clockwise.
C)There is no induced current in this coil.
D)The current flows clockwise initially, and then it flows counterclockwise before stopping.

Accepted Answer

According to Faraday's law of electromagnetic induction, a changing magnetic field will induce an electromotive force (EMF) in a closed loop of wire, which in turn will cause an induced current to flow through the loop. The direction of the induced current can be determined using Lenz's law, which states that the direction of the induced current will be such that it opposes the change in magnetic flux that produced it.

In this scenario, the magnetic field suddenly vanishes, which means that the magnetic flux through the coil is decreasing. To oppose this decrease in flux, the induced current in the coil must produce a magnetic field that points in the opposite direction. By using the right-hand rule for determining the direction of the magnetic field around a current-carrying wire, we can conclude that the induced current must flow counterclockwise when viewed from above. Therefore, the best choice is A) The induced current flows counterclockwise.

Question 6

A coil lies flat on a horizontal tabletop in a region where the $\vec { B }$ field points straight down.The magnetic field disappears suddenly.When viewed from above,what is the direction of the induced current in this coil as the field disappears?
A)counterclockwise
B)clockwise
C)clockwise initially, then counterclockwise before stopping
D)There is no induced current in this coil.

Accepted Answer

The answer of A coil lies flat on a horizontal...

Question 7

A bar magnet is oriented above a copper ring,as shown in the figure.The magnet is dropped and passes completely through the ring.As viewed from above,what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it? 
A)There is no current in the ring.
B)counterclockwise
C)clockwise

Accepted Answer

The answer of A bar magnet is oriented above a...

Question 8

A circular coil lies flat on a horizontal surface.A bar magnet is held fixed above the center of the coil with its north pole pointing downward.What is the direction of the induced current in the coil,as viewed from above?
A)clockwise
B)counterclockwise
C)There is no current in the coil.

Accepted Answer

There is no induced current in the coil because the magnetic field from the bar magnet is static and not changing, and there is no relative motion between the coil and the magnet. Induced current requires a changing magnetic field or relative motion.

Question 9

A circular coil of copper wire is lying flat on a horizontal table.A bar magnet is held above the center of the coil with its south pole downward.The magnet and the coil are now both raised upward with the same velocities.As viewed from above,what is the direction of the current induced in the coil as the magnet approaches the coil?
A)counterclockwise
B)clockwise
C)No current is induced in the coil.
D)An emf but no current is induced in the coil.

Accepted Answer

The answer of A circular coil of copper wire is...

Question 10

A circular coil of copper wire is lying flat on a horizontal table.A bar magnet is held above the center of the coil with its south pole downward.The magnet is released from rest and falls toward the coil.As viewed from above,what is the direction of the current induced in the coil as the magnet approaches the coil?
A)counterclockwise
B)clockwise
C)No current is induced in the coil.
D)An emf but no current is induced in the coil.

Accepted Answer

As the south pole of the magnet approaches the coil, it creates a magnetic field that passes through the coil. This change in magnetic field induces a current in the coil according to Faraday's law of electromagnetic induction. The induced current creates a magnetic field that opposes the motion of the magnet, which means the magnetic field lines from the induced current must be in the opposite direction of the magnetic field lines from the approaching magnet. By applying the right-hand rule to the induced magnetic field lines, we can see that the direction of the induced current is clockwise.

Question 11

A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is kept fixed while the ring is dropped,what is the direction of the current induced in the ring,as viewed from below the ring? 
A)There is no current in the ring.
B)counterclockwise
C)clockwise

Accepted Answer

According to Faraday's law of electromagnetic induction, a changing magnetic field induces an electric field, which in turn produces a current. In this case, as the ring is dropped, the magnetic field passing through the ring changes, and therefore an electric field and current are induced. By Lenz's law, the direction of the induced current opposes the change that produced it, which in this case is the decrease in magnetic flux through the ring. From below the ring, the magnetic field lines appear to be entering the ring from the left and exiting from the right. Therefore, the induced current must create a magnetic field that opposes this change. This can be achieved by creating a magnetic field that enters from the right and exits from the left, which corresponds to a clockwise current flow as viewed from below the ring. Therefore, the correct answer is C.

Question 12

According to Lenz's law,the induced current in a circuit always flows to oppose the external magnetic flux through the circuit.

Accepted Answer

The answer of According to Lenz's law,the induced current in...

Question 13

A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is pulled upward,what is the direction of the current induced in the ring,as viewed from above? 
A)There is no current in the ring.
B)counterclockwise
C)clockwise

Accepted Answer

The answer of A bar magnet is oriented above a...

Question 14

A bar magnet is close to a solenoid,as shown in the figure.As viewed through the solenoid looking toward the magnet,what is the direction (clockwise or counterclockwise)of the current (if any)induced in the solenoid in each case?
(a)The magnet is pushed toward the solenoid.
(b)The magnet and solenoid both move to the right at 25 cm/s.

Accepted Answer

The answer of A bar magnet is close to a...

Question 15

According to Faraday's law,a coil in a strong magnetic field must have a greater induced emf in it than a coil in a weak magnetic field.

Accepted Answer

The answer of According to Faraday's law,a coil in a...

Question 16

A circular coil lies flat on a horizontal surface.A bar magnet is held above the center of the coil with its north pole pointing down.If the magnet is dropped from this position what is the direction of the induced current in the coil,as viewed from above?
A)counterclockwise
B)clockwise
C)An emf but no current is induced in the coil.
D)There is no current in the coil.

Accepted Answer

According to Lenz's law, the direction of the induced current in the coil will be such that it opposes the change that caused it. As the north pole of the magnet approaches the coil, the coil will induce a current that creates a magnetic field opposing the magnet's approach. This means the coil will act like a magnet with a north pole facing up towards the falling magnet's north pole. To create such a magnetic field, the current must flow counterclockwise when viewed from above.

Question 17

At a certain instant,coil A is in a 10-T external magnetic field and coil B is in a 1-T external magnetic field.Both coils have the same area and are oriented at right angles to the field.Which coil will have a greater emf induced in it?
A)coil A
B)coil B
C)It is impossible to know without more information about the fields.

Accepted Answer

The answer of At a certain instant,coil A is in...

Question 18

A long straight wire lies on a horizontal table and carries an ever-increasing current toward the north.Two coils of wire lie flat on the table,one on either side of the wire.When viewed from above,the direction of the induced current in these coils is
A)clockwise in both coils.
B)counterclockwise in both coils.
C)clockwise in the east coil and counterclockwise in the west coil.
D)counterclockwise in the east coil and clockwise in the west coil.

Accepted Answer

According to Faraday's law of electromagnetic induction, an increasing current in a nearby wire will induce a current in a nearby coil in a direction such that the induced magnetic field opposes the change in the original magnetic field. In this case, the increasing current in the straight wire induces a magnetic field that points towards the north. To oppose this, the induced current in the coils must create a magnetic field that points towards the south. Using the right-hand rule for determining the direction of the magnetic field around a current-carrying wire, we can see that the induced current in the east coil must flow counterclockwise, while the induced current in the west coil must flow clockwise. Therefore, the answer is D, counterclockwise in the east coil and clockwise in the west coil.

Question 19

According to Lenz's law,the induced current in a circuit always flows to oppose the external magnetic field through the circuit.

Accepted Answer

The answer of According to Lenz's law,the induced current in...

Question 20

A coil lies flat on a level tabletop in a region where the $\vec { B }$ field vector points straight up.The $\vec { B }$ field suddenly grows stronger in magnitude.When viewed from above,what is the direction of the induced current in this coil as the field increases?
A)counterclockwise
B)clockwise
C)clockwise initially, then counterclockwise before stopping
D)There is no induced current in this coil.

Accepted Answer

According to Faraday's law, a changing magnetic field induces an electromotive force (emf) that produces an electric current in a closed loop. The direction of the induced current is given by Lenz's law, which states that the induced current flows in such a way as to oppose the change in the magnetic field that produced it. In this case, as the magnetic field suddenly grows stronger, the induced current will flow in a way to produce a magnetic field that opposes the increase in the original field. That means, the induced current will generate a magnetic field that points downwards. By the right-hand rule, the induced current should flow in a clockwise direction to create a magnetic field pointing downwards. Therefore, the answer is B clockwise.

Quiz 19: Electromagnetic Induction

Two solenoids are close to each other,as shown in the figure,with the switch S open.When the switch is suddenly closed,which way will the induced current flow through the galvanometer in the left-hand solenoid?

An outer metal ring surrounds an inner metal ring,as shown in the figure.The current in the outer ring is counterclockwise and decreasing.What is the direction of the induced current in the inner ring?

A flat coil is in a uniform magnetic field.The magnetic flux through the coil is greatest when the plane of its area is

A coil lies flat on a tabletop in a region where the B⃗\vec { B }B field vector points straight up.The magnetic field vanishes suddenly.When viewed from above,what is the sense of the induced current in this coil as the field fades?

A coil lies flat on a horizontal tabletop in a region where the B⃗\vec { B }B field points straight down.The magnetic field disappears suddenly.When viewed from above,what is the direction of the induced current in this coil as the field disappears?

A bar magnet is oriented above a copper ring,as shown in the figure.The magnet is dropped and passes completely through the ring.As viewed from above,what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it?

A circular coil lies flat on a horizontal surface.A bar magnet is held fixed above the center of the coil with its north pole pointing downward.What is the direction of the induced current in the coil,as viewed from above?

A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is kept fixed while the ring is dropped,what is the direction of the current induced in the ring,as viewed from below the ring?

According to Lenz's law,the induced current in a circuit always flows to oppose the external magnetic flux through the circuit.

A bar magnet is oriented above a copper ring,as shown in the figure.If the magnet is pulled upward,what is the direction of the current induced in the ring,as viewed from above?

According to Faraday's law,a coil in a strong magnetic field must have a greater induced emf in it than a coil in a weak magnetic field.

A circular coil lies flat on a horizontal surface.A bar magnet is held above the center of the coil with its north pole pointing down.If the magnet is dropped from this position what is the direction of the induced current in the coil,as viewed from above?

At a certain instant,coil A is in a 10-T external magnetic field and coil B is in a 1-T external magnetic field.Both coils have the same area and are oriented at right angles to the field.Which coil will have a greater emf induced in it?

A long straight wire lies on a horizontal table and carries an ever-increasing current toward the north.Two coils of wire lie flat on the table,one on either side of the wire.When viewed from above,the direction of the induced current in these coils is

According to Lenz's law,the induced current in a circuit always flows to oppose the external magnetic field through the circuit.

A coil lies flat on a level tabletop in a region where the B⃗\vec { B }B field vector points straight up.The B⃗\vec { B }B field suddenly grows stronger in magnitude.When viewed from above,what is the direction of the induced current in this coil as the field increases?

A coil lies flat on a tabletop in a region where the $\vec { B }$ field vector points straight up.The magnetic field vanishes suddenly.When viewed from above,what is the sense of the induced current in this coil as the field fades?

A coil lies flat on a horizontal tabletop in a region where the $\vec { B }$ field points straight down.The magnetic field disappears suddenly.When viewed from above,what is the direction of the induced current in this coil as the field disappears?

A coil lies flat on a level tabletop in a region where the $\vec { B }$ field vector points straight up.The $\vec { B }$ field suddenly grows stronger in magnitude.When viewed from above,what is the direction of the induced current in this coil as the field increases?