Question 1

If the induced current in a wire loop were such that the flux it produces were in the same direction as the change in external flux causing the current, which of the following conservation laws would end up being violated?

Accepted Answer

According to Faraday's law of induction, the induced emf is equal to the negative rate of change of magnetic flux through a surface. If the induced current produces a flux in the same direction as the change in external flux causing the current, the total flux through the surface would increase, violating the conservation of energy. This would indicate that energy is being created out of nothing, which is not possible according to the law of conservation of energy.

Question 2

A straight wire of length  is oriented east-west and is in a magnetic field B pointing north.The wire is moving downward at a constant speed v.Which end of the rod is positively charged?

Accepted Answer

The answer of A straight wire of length  is...

Question 3

A 500-turn circular coil with an area of 0.050 0 m² is mounted on a rotating frame that turns at a rate of 20.0 rad/s in the presence of a 0.050 0-T uniform magnetic field that is perpendicular to the axis of rotation.What is the instantaneous emf in the coil at the moment that the normal to its plane is at a 30.0$\degree$ angle to the field?

Accepted Answer

The answer of A 500-turn circular coil with an area...

Question 4

A bar magnet is falling through a loop of wire with constant velocity.The north pole enters first.The induced current will be greatest in magnitude when the magnet is located so that:

Accepted Answer

The induced current will be greatest when the magnetic flux through the loop changes the most. This occurs when the magnet is near the north or south pole, as the magnetic field is strongest at these locations and changes quickly as the magnet moves past the loop. In contrast, the magnetic field is nearly constant near the middle of the magnet, so the induced current is weaker. Choice D is not relevant as the problem already specifies that the magnet is moving at constant velocity, so there is no acceleration to consider.

Question 5

The basic function of the electric generator is which of the following conversion processes?

Accepted Answer

The basic function of an electric generator is to convert mechanical energy into electrical energy. This is done by using a rotating shaft to turn a magnetic field within a wire coil, which generates an electrical current. Therefore, choice A is the correct answer.

Question 6

The operation of an electric motor depends on which of the following effects?

Accepted Answer

The operation of an electric motor depends on the force acting on a current-carrying wire in a magnetic field, known as the Lorentz force. The force causes the wire to rotate and thus operates the motor. The other options, Doppler effect and photoelectric effect, are not related to the operation of an electric motor. Option D is similar to option C, but it is not complete as it only describes one part of the operation.

Question 7

Two loops of wire are arranged so that a changing current in one will induce a current in the other.If the current in the first is increasing clockwise by 1.0 A every second, the induced current in the second loop will:

Accepted Answer

The answer of Two loops of wire are arranged so...

Question 8

If a bar magnet is falling through a loop of wire, the induced current in the loop of wire sets up a field which exerts a force on the magnet.This force between the magnet and the loop will be attractive when:

Accepted Answer

When the magnet is entering the loop, the induced current initially opposes the motion of the magnet, resulting in a repulsive force. When the magnet is halfway through, the induced current is maximum and the force is zero. When the magnet is leaving the loop, the induced current opposes the decrease in the magnetic field, resulting in an attractive force between the magnet and the loop. Therefore, the best choice is C).

Question 9

A bar magnet is falling through a loop of wire with constant velocity.The north pole enters first.As the south pole leaves the loop of wire, the induced current (as viewed from above) will be:

Accepted Answer

When the north pole (positive end) of the magnet enters the loop of wire, it induces a counterclockwise current to oppose the changing magnetic field. As the magnet falls, the magnetic field decreases (since it is moving further away from the loop) and induces a clockwise current to oppose the change. This current will continue until the south pole (negative end) of the magnet leaves the loop.

Question 10

A straight wire of length  is oriented east-west and is in a magnetic field B pointing north.The wire is moving downward at a constant speed v.If the resistance of the rod is R, what is the current through the rod?

Accepted Answer

The answer of A straight wire of length  is...

Question 11

The wiring in a motor has resistance of 3.0 W and produces a back emf of 1.0 V when connected to a 9.0-V battery of negligible resistance.Find the current flow through the motor.

Accepted Answer

The answer of The wiring in a motor has resistance...

Question 12

A 500-turn circular coil with an area of 0.050 0 m² is mounted on a rotating frame, which turns at a rate of 20.0 rad/s in the presence of a 0.050 0-T uniform magnetic field that is perpendicular to the axis of rotation.What is the instantaneous emf in the coil at the moment that the normal to its plane is at a 90.0$\degree$ angle to the field?

Accepted Answer

The answer of A 500-turn circular coil with an area...

Question 13

The "back emf" of a motor refers to a source of voltage that:

Accepted Answer

The answer of The "back emf" of a motor refers...

Question 14

A 500-turn circular coil with an area of 0.050 0 m² is mounted on a rotating frame, which turns at a rate of 20.0 rad/s in the presence of a 0.050 0-T uniform magnetic field that is perpendicular to the axis of rotation.What is the instantaneous emf in the coil at the moment that the normal to its plane is parallel to the field?

Accepted Answer

The answer of A 500-turn circular coil with an area...

Question 15

A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where the magnetic field of the earth is 60 µT directed 50$\degree$ below the horizontal.What is the magnitude of the induced emf between the ends of the wing?

Accepted Answer

The induced emf between the ends of the wing can be calculated using the formula: 
emf = (B x L x v x sinθ) 
where B is the magnetic field strength, L is the length of the wing (which we can assume to be equal to its wingspan), v is the velocity of the plane, and θ is the angle between the magnetic field and the plane's velocity vector. 
Substituting the given values, we get: 
emf = (60 x 10^-6 T) x (40 m) x (300 m/s) x sin(50°) 
emf = 0.55 V or 550 mV (rounded to 3 significant figures) 
Therefore, the correct choice is (C).

Question 16

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when:

Accepted Answer

The answer of Electricity may be generated by rotating a...

Question 17

A motor with a coil resistance of 10 W is attached to a voltage supply of 90 V.What is the current in the motor when it is running at its maximum speed with a back emf of 60 V?

Accepted Answer

The answer of A motor with a coil resistance of...

Question 18

The function of the electric motor is which one of the following conversion processes?

Accepted Answer

The electric motor converts electrical energy into mechanical energy, making it capable of performing mechanical work.

Question 19

The back emf in an electric motor is its maximum value under which condition?

Accepted Answer

Back emf is the voltage generated in a motor due to its rotation. It is directly proportional to the speed of the motor. Therefore, the maximum value of back emf will occur when the motor speed is at its maximum.

Question 20

The operation of a tape player to play music depends on which of the following?

Accepted Answer

The operation of a tape player to play music depends on induced current from the motion of a magnet past a wire, which is known as electromagnetic induction. As the tape passes over the playback head, the magnetic field on the tape induces a current in the wire coils of the head, which is then amplified and sent to the speakers.

Quiz 20: Induced Voltages and Inductance

If the induced current in a wire loop were such that the flux it produces were in the same direction as the change in external flux causing the current, which of the following conservation laws would end up being violated?

A straight wire of length is oriented east-west and is in a magnetic field B pointing north.The wire is moving downward at a constant speed v.Which end of the rod is positively charged?

A bar magnet is falling through a loop of wire with constant velocity.The north pole enters first.The induced current will be greatest in magnitude when the magnet is located so that:

The basic function of the electric generator is which of the following conversion processes?

The operation of an electric motor depends on which of the following effects?

Two loops of wire are arranged so that a changing current in one will induce a current in the other.If the current in the first is increasing clockwise by 1.0 A every second, the induced current in the second loop will:

If a bar magnet is falling through a loop of wire, the induced current in the loop of wire sets up a field which exerts a force on the magnet.This force between the magnet and the loop will be attractive when:

A bar magnet is falling through a loop of wire with constant velocity.The north pole enters first.As the south pole leaves the loop of wire, the induced current (as viewed from above) will be:

A straight wire of length is oriented east-west and is in a magnetic field B pointing north.The wire is moving downward at a constant speed v.If the resistance of the rod is R, what is the current through the rod?

The wiring in a motor has resistance of 3.0 W and produces a back emf of 1.0 V when connected to a 9.0-V battery of negligible resistance.Find the current flow through the motor.

The "back emf" of a motor refers to a source of voltage that:

A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where the magnetic field of the earth is 60 µT directed 50 $\degree$ below the horizontal.What is the magnitude of the induced emf between the ends of the wing?

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when:

A motor with a coil resistance of 10 W is attached to a voltage supply of 90 V.What is the current in the motor when it is running at its maximum speed with a back emf of 60 V?

The function of the electric motor is which one of the following conversion processes?

The back emf in an electric motor is its maximum value under which condition?

The operation of a tape player to play music depends on which of the following?

Quiz 20: Induced Voltages and Inductance

If the induced current in a wire loop were such that the flux it produces were in the same direction as the change in external flux causing the current, which of the following conservation laws would end up being violated?

A straight wire of length is oriented east-west and is in a magnetic field B pointing north.The wire is moving downward at a constant speed v.Which end of the rod is positively charged?

A bar magnet is falling through a loop of wire with constant velocity.The north pole enters first.The induced current will be greatest in magnitude when the magnet is located so that:

The basic function of the electric generator is which of the following conversion processes?

The operation of an electric motor depends on which of the following effects?

Two loops of wire are arranged so that a changing current in one will induce a current in the other.If the current in the first is increasing clockwise by 1.0 A every second, the induced current in the second loop will:

If a bar magnet is falling through a loop of wire, the induced current in the loop of wire sets up a field which exerts a force on the magnet.This force between the magnet and the loop will be attractive when:

A bar magnet is falling through a loop of wire with constant velocity.The north pole enters first.As the south pole leaves the loop of wire, the induced current (as viewed from above) will be:

A straight wire of length is oriented east-west and is in a magnetic field B pointing north.The wire is moving downward at a constant speed v.If the resistance of the rod is R, what is the current through the rod?

The wiring in a motor has resistance of 3.0 W and produces a back emf of 1.0 V when connected to a 9.0-V battery of negligible resistance.Find the current flow through the motor.

The "back emf" of a motor refers to a source of voltage that:

A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where the magnetic field of the earth is 60 µT directed 50 °\degree° below the horizontal.What is the magnitude of the induced emf between the ends of the wing?

Electricity may be generated by rotating a loop of wire between the poles of a magnet.The induced current is greatest when:

A motor with a coil resistance of 10 W is attached to a voltage supply of 90 V.What is the current in the motor when it is running at its maximum speed with a back emf of 60 V?

The function of the electric motor is which one of the following conversion processes?

The back emf in an electric motor is its maximum value under which condition?

The operation of a tape player to play music depends on which of the following?

A large jetliner with a wingspan of 40 m flies horizontally and due north at a speed of 300 m/s in a region where the magnetic field of the earth is 60 µT directed 50 $\degree$ below the horizontal.What is the magnitude of the induced emf between the ends of the wing?