Magnetism and Magnetic Dipole Moments

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Questions and Answers

What is the Curie temperature for iron?

900 K

860 K

1043 K (correct)

770 K

What occurs when attempts are made to separate north and south poles in a magnet?

They form additional poles.

They become randomly aligned.

They can be separated indefinitely.

They result in pairs of poles. (correct)

What is a consequence of lowering the temperature of ferromagnetic materials?

Formation of Curie domains. (correct)

Permanent loss of magnetism.

Increased random alignment of domains.

Splitting of the magnet occurs.

What happens to the magnetic properties of iron atoms at temperatures above the Curie temperature?

They lose their magnetic properties. Signup and view all the answers

What happens when a magnet is shrunk down to one iron atom?

It contains both a north pole and a south pole. Signup and view all the answers

What type of force do permanent magnets exert?

Magnetic force Signup and view all the answers

What happens when a permanent magnet is split?

Two smaller magnets remain Signup and view all the answers

What is true about magnetic monopoles based on current understanding?

They are only hypothetical and not yet discovered Signup and view all the answers

Which statement best describes the nature of magnets?

They have both North and South poles Signup and view all the answers

What could be a significant outcome if magnetic monopoles were discovered?

They would introduce symmetry to electric charge Signup and view all the answers

Which equation represents the divergence of the electric field?

$∇⋅E = \frac{\rho}{\epsilon_0}$ Signup and view all the answers

What does the equation $∇×B = \mu_0 J + \mu_0 \epsilon_0 \frac{\partial E}{\partial t}$ signify in the context of electromagnetism?

The relationship between electric and magnetic fields during induction Signup and view all the answers

Which of the following topics is NOT included in the syllabus for PHY1032S?

Angular Momentum Signup and view all the answers

In the context of magnetism, what does 'spatial thinking' refer to?

The inherent three-dimensional nature of magnetic interactions Signup and view all the answers

What is recommended as a strategy for success in the course?

Consistent self-study corresponding to lecture hours Signup and view all the answers

What is the proper method for submitting weekly problem sets?

Submission by Friday at 10:00 AM Signup and view all the answers

Which statement about alternating current (AC) circuits is true?

AC is relevant in household electricity and the power grid. Signup and view all the answers

What does the term 'compartmentalization of knowledge' imply in the study of physics?

Different areas of physics and mathematics are interlinked. Signup and view all the answers

What does the torque on a magnetic dipole depend on?

The magnetic dipole moment and the magnetic field Signup and view all the answers

At which angle does the maximum torque occur for a magnetic dipole?

90 degrees Signup and view all the answers

What is the outcome when a coil rotates past the equilibrium at 0 degrees?

The torque reverses direction Signup and view all the answers

How can the coil in an electric motor continue to rotate in the same direction?

Reversing the current at 0 degrees Signup and view all the answers

Which of the following describes the magnetic dipole moment?

It is a property shared by bar magnets and solenoids Signup and view all the answers

What happens to the torque on the dipole as it rotates towards an angle of 0 degrees?

It decreases to zero Signup and view all the answers

What is the unit of torque used in the context of magnetic dipoles?

Newton-meter Signup and view all the answers

If the magnetic dipole moment is aligned perfectly with the magnetic field, what is the torque?

Zero torque Signup and view all the answers

What is the relationship between the magnetic force and the velocity of a charged particle?

The magnetic force is always perpendicular to the velocity. Signup and view all the answers

Which equation correctly represents the balance of magnetic and centripetal forces for a charged particle in circular motion?

$qvB = mv_{ot}^2/r$ Signup and view all the answers

How is the radius of the circular path of a charged particle in a magnetic field determined?

By the product of mass and velocity divided by charge and magnetic field strength. Signup and view all the answers

In the context of motion in a magnetic field, what component of velocity does not experience any force?

The component parallel to the magnetic field. Signup and view all the answers

What is the shape of the path taken by a charged particle moving in a magnetic field?

Helical path Signup and view all the answers

Which term describes the motion characterized by the combination of parallel and perpendicular velocities in a magnetic field?

Helical motion Signup and view all the answers

What is the effect of increasing the charge (q) on the radius of the circular path described by a charged particle in a magnetic field?

The radius increases. Signup and view all the answers

Which of the following factors does NOT affect the motion of a charged particle in a magnetic field?

The color of the particle Signup and view all the answers

Study Notes

Magnetism

Magnetism is a long-range force that can be attractive or repulsive.
Magnets always have two poles: North and South.
When a magnet is split, two smaller magnets remain.
The force between magnets is not the same as the electric force.
Magnetic forces do not affect stationary charged objects.
Magnets are not electrically charged.
Magnetic monopoles are hypothetical particles that have only a single magnetic pole (North or South), but no experimental evidence has been found.

Magnetic Dipole Moment

The concept of a magnetic dipole moment (m) applies to bar magnets, solenoids, and loops.
Torque on a dipole is given by: "τ = m × B"
The torque on a dipole aligns the magnetic dipole moment with the magnetic field.
The maximum torque is achieved when the angle between the magnetic dipole moment and the magnetic field is 90 degrees (sin θ = 1).

The Electric Motor

Uses magnetic torque to produce continuous rotation.
The torque on a coil reverses direction as the coil rotates past the equilibrium position (θ = 0).
To ensure continuous rotation, brushes automatically reverse the current as the coil passes through θ = 0.

Charged Particle In a Magnetic Field

The magnetic force is always perpendicular to the velocity of a charged particle moving in a magnetic field.
This force causes a charged particle to move in a circular path whose radius depends on the particle's velocity, charge, and the magnetic field strength.

Motion of a Charged Particle in a Magnetic Field

Charged particles in a magnetic field experience a force that causes them to follow a helical path.
The particle moves in a circular path perpendicular to the magnetic field and with a constant velocity parallel to the magnetic field.
The radius of the circular path is given by: "r = mv⊥ / qB"

Mass Spectrometer

Uses magnetic fields to separate particles with different masses and charges.
The motion of a charged particle in a magnetic field is determined by its charge (q), mass (m), and velocity (v).

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Description

Explore the fundamentals of magnetism, including the properties of magnets, magnetic dipole moments, and the functioning of electric motors. This quiz covers the key concepts surrounding magnetic forces and their applications in technology. Test your understanding of how magnetic torque influences rotation in devices like electric motors.