An electron is launched with velocity in a uniform magnetic field .The angle $\theta$0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:

A) 2$\pi$m/eB B) 2$\pi$mv/eB C) 2$\pi$mv sin$\theta$/eB D) 2$\pi$mv cos$\theta$/eB E) none of these A) 2$\pi$m/eB B) 2$\pi$mv/eB C) 2$\pi$mv sin$\theta$/eB D) 2$\pi$mv cos$\theta$/eB E) none of these

A) must be perpendicular to but not necessarily to B) must be perpendicular to but not necessarily to C) must be perpendicular to but not necessarily to D) all three vectors must be mutually perpendicular E) must be perpendicular to both and A) must be perpendicular to but not necessarily to B) must be perpendicular to but not necessarily to C) must be perpendicular to but not necessarily to D) all three vectors must be mutually perpendicular E) must be perpendicular to both and

A loop of current-carrying wire has a magnetic dipole moment of 5.0 *10-4 A.m2.If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

A) -9.5 x 10-5 J B) -1.5 x 10-4 J C) -1.8 x 10-4 J D) +1.5 x 10-4 J E) +9.5 x 10-5 J A) -9.5 x 10-5 J B) -1.5 x 10-4 J C) -1.8 x 10-4 J D) +1.5 x 10-4 J E) +9.5 x 10-5 J

Exam 28: Magnetic Fields

The diagram shows a straight wire carrying a flow of electrons into the page.The wire is between the poles of a permanent magnet.The direction of the magnetic force exerted on the wire is:

(Multiple Choice)

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Question 21

A beam of electrons is sent horizontally down the axis of a tube to strike a fluorescent screen at the end of the tube.On the way, the electrons encounter a magnetic field directed vertically downward.The spot on the screen will therefore be deflected:

(Multiple Choice)

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Question 22

An electron moves in the negative x direction, through a uniform magnetic field that is in the negative y direction.The magnetic force on the electron is:

(Multiple Choice)

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Question 23

The figure shows the motion of electrons in a wire which is near the N pole of a magnet.The wire will be pushed:

(Multiple Choice)

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Question 24

A hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north.It will be deflected:

(Multiple Choice)

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Question 25

The current is from left to right in the conductor shown.The magnetic field is into the page and point S is at a higher potential than point T.The charge carriers are:

(Multiple Choice)

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Question 26

A current is clockwise around the outside edge of this page and a uniform magnetic field is directed parallel to the page, from left to right.If the magnetic force is the only force acting on the page, the page will rotate so the right edge:

(Multiple Choice)

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Question 27

An electron is launched with velocity $An electron is launched with velocity in a uniform magnetic field .The angle \theta 0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:$ in a uniform magnetic field $An electron is launched with velocity in a uniform magnetic field .The angle \theta 0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:$ .The angle $\theta$ 0between $An electron is launched with velocity in a uniform magnetic field .The angle \theta 0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:$ and $An electron is launched with velocity in a uniform magnetic field .The angle \theta 0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:$ is between 0 and 90^o.As a result, the electron follows a helix, its velocity vector $An electron is launched with velocity in a uniform magnetic field .The angle \theta 0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:$ returning to its initial value in a time interval of:

(Multiple Choice)

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Question 28

In the formula :

(Multiple Choice)

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Question 29

J.J.Thomson's experiment, involving the motion of an electron beam in mutually perpendicular and fields, gave the value of:

(Multiple Choice)

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Question 30

The units of magnetic dipole moment are:

(Multiple Choice)

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Question 31

An electron and a proton are both initially moving with the same speed and in the same direction at 90˚ to the same uniform magnetic field.They experience magnetic forces, which are initially:

(Multiple Choice)

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Question 32

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field .For which of these is the potential energy the greatest?

(Multiple Choice)

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Question 33

An electron is moving north in a region where the magnetic field is south.The magnetic force exerted on the electron is:

(Multiple Choice)

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Question 34

The magnetic torque exerted on a flat current-carrying loop of wire by a uniform magnetic field is:

(Multiple Choice)

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Question 35

At any point the magnetic field lines are in the direction of:

(Multiple Choice)

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Question 36

An electron is travelling in the positive x direction.A uniform electric field is in the negative y direction.If a uniform magnetic field with the appropriate magnitude and direction also exists in the region, the total force on the electron will be zero.The appropriate direction for the magnetic field is:

(Multiple Choice)

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Question 37

Electrons (mass m, charge -e)are accelerated from rest through a potential difference V and are then deflected by a magnetic field that is perpendicular to their velocity.The radius of the resulting electron trajectory is:

(Multiple Choice)

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Question 38

A loop of current-carrying wire has a magnetic dipole moment of 5.0 *10^-4 A.m².If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

(Multiple Choice)

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Question 39

The magnetic dipole moment of a current-carrying loop of wire is in the positive z direction.If a uniform magnetic field is in the positive x direction the magnetic torque on the loop is:

(Multiple Choice)

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Question 40

Showing 21 - 40 of 53

Exam 28: Magnetic Fields

The diagram shows a straight wire carrying a flow of electrons into the page.The wire is between the poles of a permanent magnet.The direction of the magnetic force exerted on the wire is:

A beam of electrons is sent horizontally down the axis of a tube to strike a fluorescent screen at the end of the tube.On the way, the electrons encounter a magnetic field directed vertically downward.The spot on the screen will therefore be deflected:

An electron moves in the negative x direction, through a uniform magnetic field that is in the negative y direction.The magnetic force on the electron is:

The figure shows the motion of electrons in a wire which is near the N pole of a magnet.The wire will be pushed:

A hydrogen atom that has lost its electron is moving east in a region where the magnetic field is directed from south to north.It will be deflected:

The current is from left to right in the conductor shown.The magnetic field is into the page and point S is at a higher potential than point T.The charge carriers are:

A current is clockwise around the outside edge of this page and a uniform magnetic field is directed parallel to the page, from left to right.If the magnetic force is the only force acting on the page, the page will rotate so the right edge:

An electron is launched with velocity in a uniform magnetic field .The angle θ\thetaθ 0between and is between 0 and 90o.As a result, the electron follows a helix, its velocity vector returning to its initial value in a time interval of:

In the formula :

J.J.Thomson's experiment, involving the motion of an electron beam in mutually perpendicular and fields, gave the value of:

The units of magnetic dipole moment are:

An electron and a proton are both initially moving with the same speed and in the same direction at 90˚ to the same uniform magnetic field.They experience magnetic forces, which are initially:

The diagrams show five possible orientations of a magnetic dipole in a uniform magnetic field .For which of these is the potential energy the greatest?

An electron is moving north in a region where the magnetic field is south.The magnetic force exerted on the electron is:

The magnetic torque exerted on a flat current-carrying loop of wire by a uniform magnetic field is:

At any point the magnetic field lines are in the direction of:

Electrons (mass m, charge -e)are accelerated from rest through a potential difference V and are then deflected by a magnetic field that is perpendicular to their velocity.The radius of the resulting electron trajectory is:

A loop of current-carrying wire has a magnetic dipole moment of 5.0 *10-4 A.m2.If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?

The magnetic dipole moment of a current-carrying loop of wire is in the positive z direction.If a uniform magnetic field is in the positive x direction the magnetic torque on the loop is:

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A loop of current-carrying wire has a magnetic dipole moment of 5.0 *10^-4 A.m².If the dipole moment makes an angle of 57° with a magnetic field of 0.35 T, what is its potential energy?