Magnetism

https://quizlet.com/458126220/phys-1032-exam-3-flash-cards/

What distinction does magnetism share with electricity and gravitation and why?

It is a long-range or field force because it acts at a distance without need for contact.

Because magnets exert field forces, they…

do not need to touch to exert a force on each other

Can a magnet ever be cut in half in such a way to create a magnetic monopole?

No, magnets are always in N-S pairs (unlike charges)

What kind of materials are attracted to a magnet?

Magnetic materials

What is the most common magnetic material?

Iron

To which pole of a magnet are magnetic materials attracted?

Both

Given that every magnet sets up a magnetic field in the space around itself, if a second magnet is brought into the field, what will the second magnet do if allowed to rotate?

It will tend to align with the magnetic field of the first magnet.

The direction of a magnetic field is the direction that which pole of a compass needle points?

North

To what is the torque a compass feels as it lines up with the field direction proportional to?

The strength of a magnetic field

In what direction do magnetic field vectors point?

In the direction of a compass’ needle

Magnetic field due to a long, straight wire formula.

B = ((4pi * 10^-7)(I))/(2pi(r))

Permeability constant (of free space)

4pi * 10^-7 (Tesla meters per Amp)

To calculate magnetic field at a point with multiple sources present…

add the magnetic fields moving in the same direction, and subtract the ones that are not

From where to where do the magnetic lines of a magnet travel?

From north to south

Where are the magnetic and geographic north and south poles?

North magnetic pole and geographic south pole near Antarctica, south magnetic pole and north geographic south pole near Canada

In which direction do magnetic field lines in a current loop travel?

Either clockwise or counterclockwise around the loop’s circular cross-section (with no “hole”).

What is a solenoid?

A long coil of wire with an equal current I passing through each turn

Where is the electric field a solenoid generates the strongest? Where is it the weakest?

On the inside, on the outside

Magnetic field inside the center of a coil with n turns formula

B = ((4pi *10^-7)(N)(I))/2R

How much force is on a charged particle at rest?

Zero

How much force is on an object moving parallel to a magnetic field?

None

What is the relationship between the angle between the velocity and magnetic field and the magnetic force?

Directly proportional

At what angle between the velocity and magnetic field is magnetic force the greatest?

90

Magnetic force formula of a particle in movement.

F = |q|vBsin(a)

For what thing moving through a magnetic field result in a magnetic force always perpendicular to its movement?

A charged particle

How does a magnetic field shape the trajectory of a charged particle?

It causes the particle to move in a circle

Circular motion equation (@ sin(theta) = 1)

F = (mv²)/r

Magnetic force for a charged particle moving in a magnetic field.

F = (mv²)/r = |q|vB

Radius of circular orbit for a charged particle in a magnetic field.

r = (mv)/(|q|B)

Force of an electric field on a wire.

F = ILBsina

Which way should the magnetic field lines in a loop turn?

Either towards the middle, or towards the outside (no two different directions)

Where is a current loop’s dipole?

On either side of the hole, starting at the center

Do opposites attract for the force generated by a current?

No, if two currents in a wire are running in the same direction, they will generate an attractive force (and vice-versa)

Describe how an electric motor works.

A battery passes a current through a wire called an armature that lies in a strong magnetic field. The armature feels a torque because its magnetic field aligns with the external one by rotating. Around when it aligns itself with the external field, a communicator reverses the current direction, so the armature will continue to rotate.

What properties do ferromagnetic materials have?

Strong attraction to magnets and an ability to be magnetized due to atoms with net magnetic moments that tend to line up and reinforce each other (RARE)

What causes magnetism?

The inherent magnetic moment of electrons, or that every electron, because it spins, is an electron in motion generating magnetism

Why do most atoms with many electrons not have a net magnetic moment (and, therefore, are not magnetic)?

Because their electrons’ magnetic moments occur in pairs, in opposite directions, so they cancel

What kinds of electrons give an atom a net magnetic moment?

Unpaired electrons

What is a magnet?

A piece of material with a north and south magnetic pole that generates a magnetic field and aligns parallel to an external magnetic field

What are domains?

Regions of aligned magnetic moments (in the same direction)

What is an induced magnetic moment?

A change in domain direction due to the introduction of an external magnetic field

What does a ferromagnetic material become when it is near a magnet?

A magnet

When a magnetic field is taken away, what happens to the domain structure of a ferromagnetic material if the magnet was weak?

It will generally return to its original state

When a magnetic field is taken away, what happens to the domain structure of a ferromagnetic material if the magnet was strong?

It may cause permanent orientation changes and permanently magnetize the material

What device uses the properties of induced magnetic moments?

Computer hard disc drives, to store information

Ampere’s Law (if current, then magnetic field, right hand rule, proportionality)

The magnitude of the magnetic field around a closed path is proportional to the current passing through the area (because the field radiates outwards), or B = ((4pi * 10^-7)(I))/(2pi(r)) = (4piNI)/L

Faraday’s Law

Current only flows when a magnet and a charge carrier have relative movement between them, and the emf created is directly proportional to the rate of change of magnetic flux linkage (phi*N)

(If a problem mentions a perpendicular field, then theta is 0 because it is referencing the angle of the normal(??))

Lenz’s Law (induction and direction of currents)

Moving a magnet near a coil will induce a current and an induced current always flows in a direction such that the induced magnetic field inside a coil opposes the change that produced it to keep loop flux constant/obey the law of conservation of energy.

(North pole front of the direction, coil repels forward movement, South pole front of the direction, coil opposes backward movement by attracting magnet)

How and why are voltage and emf related?

Electromotive force is equal to a battery’s voltage