Unit 12: Magnetism and Electromagnetism

Magnetic Field

A vector field that describes the magnetic force exerted on moving charges, electric currents, or magnetic materials

What creates magnetic fields?

Magnetic Dipoles (NOT MONODIPOLES)

A magnetic dipole has both a _____ and _____.

North; South

What do magnetic fields lines allow us to visualize?

Allows us to visualize the magnetic field around a magnetic dipole or a magnetic object

Magnetic field lines always point in what direction to what direction?

North to South

Bar Magnet

Composed of multple magnetic dipoles and has a north and south pole

The magnetic field inside of a bar magnet points from ______ to ______.

South; North

A compass will align itself with the ________ _____ snd show a field’s direction at a point in space.

Magnetic Field

Magnetic fields form _______ _____.

Closed Loops

How are magnetic dipoles created?

The rotational (circular) motion of electric charge carriers

Spin

Fundamental property of an electron; can be up or down

Magnetic Dipoles always occur in ______.

Pairs

Can the North and South poles be separated from each other?

No

A magnetic dipole in an external magnetic field may experience a torque from the magnetic field. This torque can cause what?

The dipole to align with magnetic field

What directions do the magnetic moments in a nonmagnetic material look like?

They point in random directions.

What do the randomly arranged magnetic dipoles do to each other?

They cancel each other out.

Do nonmagnetic materials exhibit a magnetic field?

No

Induced Magnetism

When a non-magnetic material becomes magnetized due to an external magnetic field

What happens when you break a bar magnet in half?

When a magnet breaks, it will become two magnets with a north and south pole.

The Earth’s North Pole is the magnetic _____ _____.

South Pole

Magnets always point towards the ______ pole.

South

Magnetic Probablity

Describes a substance’s ability to form internal magnetic field

Magnetic Permeability

How magnetic a material is

Permeability of Free Space

The magnetic permeability of empty space

What does it mean that the permeability of free space is relatively low?

Free space does not create an internal magnetic field

How can we determine a material’s relative permeability?

Nonmagnetic materials have relative permeability very close to what?

1

Diamagnetic Permeability

Weak and temporary where these materials are repelled by a magnent

Paramagnetic Permeability

Weak and temporary where these materials are attracted by a magnet

True or False: Paramagnetic attraction to an external magnetic field is greater than a diamagnetic repulsion.

True

Ferromagnetic Permeability

• In the presence of an external magnetic field, magnetic domains align with each other

• The internal magnetic field increases the external magnetic field

Magnetic Domains

Region in which the magnetic fields of atoms are grouped together and aligned

Biot-Savart Law

Right Hand Rule #1

More Confusing Right Hand Rule

When does a magnetic field not exert force on an object?

1. At rest

2. When velocity/current are in the same direction as the magnetic field

What will happen to an object because magnetic force is perpendicular to an object’s velocity?

• Only the object’s direction will change, not speed

• No work will be done

More Confusing Right Hand Rule #2

Since the magnetic force will always be perpendicular to the velocity, the object will move in …

Circle

How can you find out the radius of a circle an object is moves in?

Electric force will be in the same direction as what?

Electric Field

Watch Daily Video 3 in 12.2

When two magnetic fields overlap, the net magnetic field can be found through vector ________,

Addition

Right Hand Rule for Wires in Magnetic Fields

Magnetic Flux

Measure of the amount of magnetic field that passes through a given surface area

When does maximum magnetic flux occur?

When the area vector and magnetic field are pointed in the same direction or they are the opposite of each other (but note that the answer for when they are opposite of each other will be negative)

When does minimum magnetic flux occur?

When the area vector and magnetic field form a 90 degree angle. There will be 0 flux.