Download Magnetism Notes

Magnetism Notes
Historical
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Early magnets called ____________, naturally occurring iron ore magnetite
Named magnets by Greeks since they were found in the region Magnesia
Coulomb showed magnetic force has similar relationship to ____________ and ________________ forces
______________ showed electric current and magnetism related in 1820
He found electric current created __________ which would deflect a ______________
Magnetic Poles
Like electric charges, there are two types called ______ and _______ because of the way they react to the
earth’s magnetic field
Unlike electrical charges, can’t have __________ N or S pole; always have both
Like electrical charges, opposite poles _____________, like poles ___________
Forces between poles are ____________ proportional to strength of the poles, ________________
proportional to the square of distance between them.
Magnets can be as large as a planet or star, or as small as a spinning _____________
Magnetic Fields
Magnetic forces act over a distance by means of a __________, like electric and gravitational forces
Magnetic field is represented by ______________ like electric field
Field lines can be seen by using bits of _________ sprinkled on paper placed near magnet
Direction of field is direction of force on ___________ placed in field
Magnetic field lines shown as arrows going ________ of N poles, _________ S poles
Cause of Magnetism
Magnetic fields created by __________________
In common magnets, moving charges are _______________
Movement of charges in wires (electric current) creates _______________
Ferromagnetism
In most materials, magnetic effects due to motion of electrons cancel out
Some materials have several spinning electrons without an ______________ spinning partner
Called ferromagnetic from the Latin word for _____________
Magnetic Domains
Since each atom of ferromagnetic material is ___________, groups of atoms will line up together -- called
_______________
In unmagnetized iron, domains are _______________ oriented
When magnet is brought near, domains become aligned together, iron becomes ______________
Domains can be rearranged and magnetism lost by _________ or ______________
Electric Current and Magnetism
For straight wire with current, magnetic field lines form _____________________ around wire
Changing direction of current changes ________________ of magnetic field
If wire is bent into loop, magnetic field is ________________ inside loop
If more loops are added, magnetic field strength ____________ with each loop in coil
Long coil called a ______________
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If iron rod is placed inside solenoid, magnetic field is concentrated inside iron and ____________________
results
Magnetism and Moving Charges
Charged particle moving in magnetic field will experience ________________ due to interaction of two
magnetic fields
Force is greatest when motion is __________________ to external magnetic field, _____ when parallel
Direction of force is perpendicular to both ______________ and _______________ magnetic field
Electrons in ___________ are aimed to screen using magnetic fields
Earth’s magnetic field deflects incoming _______________ from sun and outer space
Current carrying wires in magnetic fields experience similar sideways force because of ____________
moving in wires
Two nearby current carrying wires will exert forces on each other because each creates a ______________
So current carrying wire will deflect a ____________ and will itself be deflected by strong external
__________________
Meters and Motors
Analog (not digital) meters use ______________ with magnets on each side to measure current:
galvanometer, ammeter, or voltmeter
Current through coil creates ______________; coil will try to line up with field of magnets
If coil is allowed to rotate, __________ can be made
As coil becomes aligned with magnets, current direction changes through ______________ and
______________
In large motors, permanent magnets replace with ____________________
_______________ is rotating coil in motor
Earth’s Magnetic Field
Thought to be caused by ______________ currents in liquid interior of planet
Geologic evidence shows magnetic field has moved around and _____________polarity
Magnetic poles don’t line up with ______________ poles
Difference between magnetic north and true north called _______________
Since north poles of magnets and compasses point to north, Earth’s north magnetic pole is really a
_________ type pole; south pole is really ________ type pole