how can we explain magnetism? do now: why does a compass point north?

How can we explain How can we explain magnetism?magnetism?

Do Now:Do Now:

Why does a compass point north?Why does a compass point north?

MagnetsMagnets•2 poles:

North and south

S N

•Cannot isolate a pole

S N S N

Like PolesLike Poles►2 like poles experience a 2 like poles experience a

force of repulsionforce of repulsion

S N N S

N S S N

Donut magnet DemoDonut magnet Demo

Unlike PolesUnlike Poles►2 unlike signs experience a 2 unlike signs experience a

force of attractionforce of attraction

N S N S

CompassCompass

►Attracted to magnetic south poleAttracted to magnetic south pole

S N

Therefore this is magnetic north

EarthEarth

► Earth is a huge Earth is a huge magnetmagnet

► So why does the So why does the north pole of a north pole of a compass point to compass point to the north pole of the north pole of the Earth?the Earth?

Magnetic South Pole

Magnetic North PoleGeographic

Geographic

Ferromagnetic substancesFerromagnetic substances

►Substances that are Substances that are naturally magneticnaturally magnetic IronIronNickelNickelCobaltCobalt

How do things become How do things become magnetized?magnetized?

Magnetism is caused by the spin of the unpaired electrons. When they spin in the same direction, they cause microscopic magnets called domains.

If all the domains are aligned, a magnet is formed.

Temporary MagnetTemporary Magnet

►Created when a ferromagnetic Created when a ferromagnetic substance is brought into close substance is brought into close proximity to an easily magnetized proximity to an easily magnetized substancesubstance

(domains temporarily align)(domains temporarily align)

►Occurs when the electrons spin in the Occurs when the electrons spin in the same directionsame direction

Magnetic Field LinesMagnetic Field Lines

If compasses are place around a magnet, we can visualize the field around the magnet.

N S

Magnetic FieldsMagnetic Fields

►Field lines are called lines Field lines are called lines of fluxof flux

►Defined as north to southDefined as north to south►Strongest where the lines Strongest where the lines of flux are closestof flux are closest

Magnetic FluxMagnetic Flux

Magnetic flux describes the lines of a magnetic field around a magnetized object.

Each magnetic flux line is equal to 1 Weber (Wb). The strength of the field, or magnetic flux density (B) is measured in Wb/m2 , or Tesla (T).

S S

If field lines point in the same direction,

N S

N S

They repel.

If field lines point in the opposite direction,

N S

NS

They attract.

►Magnetic fields are created by moving Magnetic fields are created by moving chargescharges Any time a charge moves (current) a Any time a charge moves (current) a

magnetic field is createdmagnetic field is created

►Outer Core of Earth is liquid iron and Outer Core of Earth is liquid iron and nickelnickel Ferromagnetic substances that have a Ferromagnetic substances that have a

charge and are movingcharge and are moving

So why is the Earth So why is the Earth magnetic?magnetic?

Magnetic ForceMagnetic Force

•Created when a moving charge Created when a moving charge passes through a magnetic fieldpasses through a magnetic field•Reason: Charge has a Reason: Charge has a magnetic field and it interacts magnetic field and it interacts with another magnetic fieldwith another magnetic field•Greatest force is when the Greatest force is when the charge passes perpendicular to charge passes perpendicular to the fieldthe field

Sidenote: Sidenote: DeGaussingDeGaussing

►Planes, ships move through the Earth’s Planes, ships move through the Earth’s magnetic field.magnetic field.

► Just as moving a charge through a Just as moving a charge through a magnetic field creates a force, forcing magnetic field creates a force, forcing an object to move through a magnetic an object to move through a magnetic field creates electricityfield creates electricity

►This needs to be taken into account or This needs to be taken into account or else navigational equipment gets else navigational equipment gets jacked upjacked up

Which produces the greatest Which produces the greatest force?force?

e-

B (magnetic lines of flux

B (magnetic lines of flux

B (magnetic lines of flux

e-

e-

Gamma RaysGamma Rays

►Moving charges through spaceMoving charges through space►Enter Earth’s magnetic fieldEnter Earth’s magnetic field►Magnetic force is createdMagnetic force is created►Gamma Rays get deflectedGamma Rays get deflected►The Earth is safeThe Earth is safe

►http://www.youtube.com/watch?http://www.youtube.com/watch?v=0JYkR17Ud5Qv=0JYkR17Ud5Q