Question 1

You push a permanent magnet with its north pole away from you toward a loop of conducting wire in front of you. Before the north pole enters the loop the current in the loop is:
A) zero
B) clockwise
C) counterclockwise
D) to your left
E) to your right

Accepted Answer

The answer of You push a permanent magnet with its...

Question 2

A rectangular loop of wire is placed midway between two long straight parallel conductors as shown. The conductors carry currents i₁ and i₂ as indicated. If i₁ is increasing and i₂ is constant, then the induced current in the loop is: A) zero B) clockwise C) counterclockwise D) depends on i₁ - i₂ E) depends on i₁ + i₂

Accepted Answer

The changing current in the left conductor will produce a changing magnetic flux, which will induce a current in the loop in such a direction as to oppose the change in flux. By applying the right-hand rule, we can see that the induced current in the loop will be counterclockwise.

Question 3

A long straight wire is in the plane of a rectangular conducting loop. The straight wire carries an increasing current in the direction shown. The current in the rectangle is: 
A) zero
B) clockwise
C) counterclockwise
D) clockwise in the left side and counterclockwise in the right side
E) counterclockwise in the left side and clockwise in the right side

Accepted Answer

According to Faraday's Law of Electromagnetic Induction, an increasing current in the wire will induce a counterclockwise current flow in the loop. Therefore, the answer is C: counterclockwise.

Question 4

At any instant of time the total magnetic flux through a stationary conducting loop is less in magnitude than the flux associated with an externally applied field. This might occur because:
A) the applied field is normal to the loop and increasing in magnitude
B) the applied field is normal to the loop and decreasing in magnitude
C) the applied field is parallel to the plane of the loop and increasing in magnitude
D) the applied field is parallel to the plane of the loop and decreasing in magnitude
E) the applied field is tangent to the loop

Accepted Answer

The answer of At any instant of time the total...

Question 5

The diagram shows a circular loop of wire that rotates at a steady rate about a diameter O that is perpendicular to a uniform magnetic field. The maximum induced emf occurs when the point X on the loop passes: 
A) a
B) b
C) c
D) d
E) e

Accepted Answer

The answer of The diagram shows a circular loop of...

Question 6

A rod with resistance R lies across frictionless conducting rails in a constant uniform magnetic field B, as shown. Assume the rails have negligible resistance. The magnitude of the force that must be applied by a person to pull the rod to the right at constant speed v is: A) 0 B) BLv C) BLv/R D) B²L²v/R E) B²Lxv/R

Accepted Answer

The answer of A rod with resistance R lies across...

Question 7

As a loop of wire with a resistance of 10  $\Omega$ moves in a constant non-uniform magnetic field, it loses kinetic energy at a uniform rate of 5 mJ/s. The induced current in the loop:
A) is 0
B) is 2 mA
C) is 2.8 mA
D) is 20 mA
E) cannot be calculated from the given data

Accepted Answer

The answer of As a loop of wire with a...

Question 8

A copper hoop is held in a vertical east-west plane in a uniform magnetic field whose field lines run along the north-south direction. The largest induced emf is produced when the hoop is:
A) rotated about a north-south axis
B) rotated about an east-west axis
C) moved rapidly, without rotation, toward the east
D) moved rapidly, without rotation, toward the south
E) moved rapidly, without rotation, toward the northwest

Accepted Answer

The induced emf is given by the equation, emf = -d(φ)/dt, where φ is the magnetic flux through the loop. 
When the hoop is rotated about a north-south axis, the flux through the loop does not change because the magnetic field is already perpendicular to the plane of the loop. 
When the hoop is moved rapidly without rotation, the flux through the loop changes due to the motion of the loop. However, the largest induced emf is produced when the area vector of the loop rotates the most with respect to the magnetic field, which occurs when the hoop is rotated about an east-west axis. Therefore, option B is the correct choice. 
Moving the hoop in any direction without rotation would not produce as large of an induced emf as rotating the hoop about an east-west axis.

Question 9

A long straight wire is in the plane of a rectangular conducting loop. The straight wire initially carries a constant current i in the direction shown. While the current i is being shut off, the current in the rectangle is: 
A) zero
B) clockwise
C) counterclockwise
D) clockwise in the left side and counterclockwise in the right side
E) counterclockwise in the left side and clockwise in the right side

Accepted Answer

The answer of A long straight wire is in the...

Question 10

A 10 turn conducting loop with a radius of 3.0 cm spins at 60 revolutions per second in a magnetic field of 0.50 T. The maximum emf generated is:
A) 0.014 V
B) 0.53 V
C) 5.3 V
D) 18 V
E) 180 V

Accepted Answer

The answer of A 10 turn conducting loop with a...

Question 11

A long straight wire is in the plane of a rectangular conducting loop. The straight wire carries a constant current i, as shown. While the wire is being moved toward the rectangle the current in the rectangle is: 
A) zero
B) clockwise
C) counterclockwise
D) clockwise in the left side and counterclockwise in the right side
E) counterclockwise in the left side and clockwise in the right side

Accepted Answer

The answer of A long straight wire is in the...

Question 12

A rectangular loop of wire is placed perpendicular to a uniform magnetic field and then spun around one of its sides at frequency f. The induced emf is a maximum when:
A) the flux is zero
B) the flux is a maximum
C) the flux is half its maximum value
D) the derivative of the flux with respect to time is zero
E) none of the above

Accepted Answer

The answer of A rectangular loop of wire is placed...

Question 13

As a loop of wire with a resistance of 10 $\Omega$ moves in a non-uniform magnetic field, it loses kinetic energy at a uniform rate of 5 mJ/s. The induced emf in the loop:
A) is 0
B) is 0.2 V
C) is 0.28 V
D) is 2 V
E) cannot be calculated from the given data

Accepted Answer

The answer of As a loop of wire with a...

Question 14

A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:
A) counterclockwise
B) clockwise
C) zero
D) up the left edge and from right to left alongthe top edge
E) throught the middle of the page

Accepted Answer

According to Lenz's law, the induced current in a closed loop will be such that its magnetic field opposes the change in the magnetic flux that produced it. Since the magnetic field is decreasing into the page, the induced current will produce a magnetic field out of the page, which can be achieved by a clockwise current flow in the loop.

Question 15

As an externally generated magnetic field through a certain conducting loop increases in magnitude, the field produced at points inside the loop by the current induced in the loop must be:
A) increasing in magnitude
B) decreasing in magnitude
C) in the same direction as the applied field
D) directed opposite to the applied field
E) perpendicular to the applied field

Accepted Answer

According to Lenz's Law, the direction of the induced current in a conductor is such that it opposes the change that produced it. Therefore, as the external magnetic field increases, the induced current in the loop must produce a magnetic field in the opposite direction. This means that the field produced at points inside the loop will also be opposite in direction to the applied field, leading to choice D as the correct answer.

Question 16

A merry-go-round has an area of 300 m² and spins at 2 rpm about a vertical axis at a place where the Earth's magnetic field is vertical and has a magnitude of 5 * 10^-⁵ T. The emf around the rim is: A) 0 B) 0.5 mV C) 3.1 mV D) 15 mV E) 30 mV

Accepted Answer

The answer of A merry-go-round has an area of 300...

Question 17

A rod of length L and electrical resistance R moves through a constant uniform magnetic field perpendicular to the rod. The force that must be applied by a person to keep the rod moving with constant velocity is: A) 0 B) BLv C) BLv/R D) B²L²v/R E) B²L²v²/R

Accepted Answer

The answer of A rod of length L and electrical...

Question 18

A copper penny slides on a horizontal frictionless table. There is a square region of constant uniform magnetic field perpendicular to the table, as shown. Which graph correctly shows the speed v of the penny as a function of time t? 
A) I
B) II
C) III
D) IV
E) V

Accepted Answer

The answer of A copper penny slides on a horizontal...

Question 19

A single loop of wire with a radius of 7.5 cm rotates about a diameter in a uniform magnetic field of 1.6 T. To produce a maximum emf of 1.0 V, it should rotate at:
A) 0
B) 2.7 rad/s
C) 5.6 rad/s
D) 35 rad/s
E) 71 rad/s

Accepted Answer

The answer of A single loop of wire with a...

Question 20

The four wire loops shown have edge lengths of either L, 2L, or 3L. They will move with the same speed into a region of uniform magnetic field  directed out of the page. Rank them according to the maximum magnitude of the induced emf, least to greatest. 
A) 1 and 2 tie, then 3 and 4 tie
B) 3 and 4 tie, then 1 and 2 tie
C) 4, 2, 3, 1
D) 1, then 2 and 3 tie, then 4
E) 1, 2, 3, 4

Accepted Answer

The answer of The four wire loops shown have edge...

Quiz 30: Induction and Inductance

You push a permanent magnet with its north pole away from you toward a loop of conducting wire in front of you. Before the north pole enters the loop the current in the loop is:

A rectangular loop of wire is placed midway between two long straight parallel conductors as shown. The conductors carry currents i1 and i2 as indicated. If i1 is increasing and i2 is constant, then the induced current in the loop is:

A long straight wire is in the plane of a rectangular conducting loop. The straight wire carries an increasing current in the direction shown. The current in the rectangle is:

At any instant of time the total magnetic flux through a stationary conducting loop is less in magnitude than the flux associated with an externally applied field. This might occur because:

The diagram shows a circular loop of wire that rotates at a steady rate about a diameter O that is perpendicular to a uniform magnetic field. The maximum induced emf occurs when the point X on the loop passes:

A rod with resistance R lies across frictionless conducting rails in a constant uniform magnetic field B, as shown. Assume the rails have negligible resistance. The magnitude of the force that must be applied by a person to pull the rod to the right at constant speed v is:

As a loop of wire with a resistance of 10 Ω\OmegaΩ moves in a constant non-uniform magnetic field, it loses kinetic energy at a uniform rate of 5 mJ/s. The induced current in the loop:

A copper hoop is held in a vertical east-west plane in a uniform magnetic field whose field lines run along the north-south direction. The largest induced emf is produced when the hoop is:

A long straight wire is in the plane of a rectangular conducting loop. The straight wire initially carries a constant current i in the direction shown. While the current i is being shut off, the current in the rectangle is:

A 10 turn conducting loop with a radius of 3.0 cm spins at 60 revolutions per second in a magnetic field of 0.50 T. The maximum emf generated is:

A long straight wire is in the plane of a rectangular conducting loop. The straight wire carries a constant current i, as shown. While the wire is being moved toward the rectangle the current in the rectangle is:

A rectangular loop of wire is placed perpendicular to a uniform magnetic field and then spun around one of its sides at frequency f. The induced emf is a maximum when:

As a loop of wire with a resistance of 10 Ω\OmegaΩ moves in a non-uniform magnetic field, it loses kinetic energy at a uniform rate of 5 mJ/s. The induced emf in the loop:

A square loop of wire lies in the plane of the page. A decreasing magnetic field is directed into the page. The induced current in the loop is:

As an externally generated magnetic field through a certain conducting loop increases in magnitude, the field produced at points inside the loop by the current induced in the loop must be:

A merry-go-round has an area of 300 m2 and spins at 2 rpm about a vertical axis at a place where the Earth's magnetic field is vertical and has a magnitude of 5 * 10-5 T. The emf around the rim is:

A rod of length L and electrical resistance R moves through a constant uniform magnetic field perpendicular to the rod. The force that must be applied by a person to keep the rod moving with constant velocity is:

A copper penny slides on a horizontal frictionless table. There is a square region of constant uniform magnetic field perpendicular to the table, as shown. Which graph correctly shows the speed v of the penny as a function of time t?

A single loop of wire with a radius of 7.5 cm rotates about a diameter in a uniform magnetic field of 1.6 T. To produce a maximum emf of 1.0 V, it should rotate at:

The four wire loops shown have edge lengths of either L, 2L, or 3L. They will move with the same speed into a region of uniform magnetic field directed out of the page. Rank them according to the maximum magnitude of the induced emf, least to greatest.

A rectangular loop of wire is placed midway between two long straight parallel conductors as shown. The conductors carry currents i₁ and i₂ as indicated. If i₁ is increasing and i₂ is constant, then the induced current in the loop is:

As a loop of wire with a resistance of 10 $\Omega$ moves in a constant non-uniform magnetic field, it loses kinetic energy at a uniform rate of 5 mJ/s. The induced current in the loop:

As a loop of wire with a resistance of 10 $\Omega$ moves in a non-uniform magnetic field, it loses kinetic energy at a uniform rate of 5 mJ/s. The induced emf in the loop:

A merry-go-round has an area of 300 m² and spins at 2 rpm about a vertical axis at a place where the Earth's magnetic field is vertical and has a magnitude of 5 * 10^-⁵ T. The emf around the rim is: