MAGNETISM
Origin of the Word
Many civilizations found lodestones.
Lodestones are objects that would attract other lodestones (metallic objects).
Magnets were named after lodestones found near Greek province Magnesia.
Magnetic Force
magnetic field
Magnet
always has 2 poles
North Pole
allowed to orient itself freely with Earth's geographic north
opposite poles attract
definition
there is a force of attraction or repulsion between like and unlike poles
permanent magnet
temporary magnet
retains magnetic properties for a long time
retains magnetic properties for short time
made of: iron cobalt etc
ex: a paper clip being magnetized by being near a nail
When is the force stronger?
the closer the poles, the greater the force
analogous to electric fields around electric charges
region around the magnet where the magnetic force acts
electrons as magnets
spinning electrons are tiny magnets
pair of spinning electrons
spinning in same direction = stronger magnet
spinning in opposite direction = work against each other
reason of most substances not being magnets
iron, nickel, cobalt - fields do not cancel entirely
Magnetic Domain
groups of atoms with aligned magnetic poles
can be demagnetized
excessive heating
passing electricity
hammering
definition = force of attraction or repulsion between like and unlike poles #
Electrostatic force and magnetic force are the same thing!
both have magnitude and direction #
symbol = B
unit = Tesla (T)
how to define
measure the force the field exerts on charged particle
can be created
with moving charges
by the spin magnetic dipole moment of electron
by the orbital magnetic dipole moment of electron
direction = where the north pole of a compass points to at that location on the field
shape of the field
shown by magnetic field lines
drawn from one pole to the other curving outward around the magnet itself
lines closer together = stronger field
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Earth as a magnet
poles
magnetic poles
differ
on opposite sides as geographic poles
always change orientation due to fluid in the earth
magnetic declination = difference between true north and magnetic north
Auroras
surround the poles of the earth
South Pole
a property of matter
north magnetic pole = aurora borealis
South Magnetic Pole = Aurora Australis
occurs when electrons in solar wind interact with elements in earth atmosphere
solar winds
leave sun at 1 million mph #
near earth
40 hours after leaving sun
follow lines of earth magnetic field
go through magnetosphere
tear drop shape
highly charged electric and magnetic fields
poles cannot be isolated
at ends/poles of magnets
in relation to a moving charge...
higher velocity
higher charge
larger magnetic field
force greatest when velocity is perpendicular to field
out of paper = dots
into paper = X s
charged particle moving in a magnetic field = deflecting force
F = BqV
F = force in Newtons
B= intensity of magnetic field in Tesla
q = charge in Couloumbs
v = velocity in meters/second
greatest when path is perpendicular to field
B = F/(qvsinr(theta))
MAGNETIC FIELD IN A CURRENT CARRYING WIRE
SINGLE WIRE
magnetic field intensity = proportional to current
direction can be determined RHR
current creates the magnetic field around the wire
PARALLEL CONDUCTING WIRES
exert forces on each other because their magnetic fields interact
current in opposite directions = wires repel
current in same direction = wires attract
Magnetic field in a current loop
RHR can be used for direction of magnetic field
SOLENOID
long helically wound coil of insulated wire
produce strong fields by combining loops
also known as electromagnets!
more coils = more overlap = Stronger magnetic field
form when current goes through loop/coil
temporary magnets
increasing strength
increase # of coils
increasing current
iron core inside coils
iron core becomes a magnet
coils have North and South ends
FORCE CAUSED BY MAGNETIC FIELD
force on wire + direction of current + direction for magnetic field = all perpendicular to each other
F = qvB = IBL*sin(theta)
I = current in Amperes
L = length in meters
using the right hand rule
fingers = magnetic field = B
palm = force = F
thumb = current = I