Transcript Magnetism and Uses

Magnetism and Uses
Goals: magnetism, source, types,
electromagnetism, magnetic materials,
force calculations, motors, generators
and transformers
Magnetism
 Magnetism – field force with north and south
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poles
Alignment of magnetic domains
Domains- groups of atoms with magnetic fields
that complement one another
Atoms exhibit magnetic properties because of
the spin of an unpaired electron (moving
electric field)
(fourth quantum number)
Opposite poles attract and the same poles repel
Field lines point away from North and toward the
South pole
Types of Magnets
 Permanent and an Electromagnet
 Permanent – hold magnetic properties domains
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are aligned bar and horseshoe
Magnetized in an electric current or a strong
magnetic field
Unmagnetized by shock, heat or another field
Diamagnetic- fields cancel no magnetism Pb
Paramagnetic- atoms are magnetic but not
domains Al
 Nonmagnetic- when permanent magnet is
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removed there is no magnetism
Ferromagnetic – strong magnetic properties Fe
Ni Co Nd
Earth and Stars
Electromagnets – coil with an iron core
Advantages – turned on and off and vary the
magnetic strength
(lab)
Turns in the coil current size of core
Why? Current - carrying conductor has a
magnetic field around it Right Hand Rule
Oersted’s discovery- with a compass and current
discovered that the current produced a magnetic
field reversed by reversing the current direction
Electromagnetism
 Magnetism produces electricity and electricity produces
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magnetism
Faraday – law of induction
Electric motors and Generators
Home wiring AC , current in opposite directions repel
magnetic fields in the same direction attract
Motors – electrical to mechanical energy
Electromagnet in the core of the motor is pushed by the
field of the electromagnet continually as the magnetic
field is reversed easier in AC
Parts include armature (moving electromagnet), rotor,
brushes, permanent magnet and commutator (switch)
(Lab)
 Generator – electric motor in reverse
 Mechanical energy into Electrical
 Energy easily moved by conductors and easily
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converted to another form
Moving coil of wire within a magnetic field
induces a current in the wire
Produces AC because of the switch in direction
of magnetic fields in the permanent magnets
Faraday’s Law of Induction – faster the solenoid
turns in the magnetic field the higher the voltage
Turbine forced to turn by wind, falling water, and
expanding steam from burning coal or nuclear
power
 Transformers – step-up or step-down
voltage to efficiently by increasing or
decreasing the number of coils around an
iron core
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V1 x N2 = V2 x N1
Magnetic Field Strength
 Electric fields produce electric force per
unit of charge E = k qq/r² E = N/C
 Magnetic fields produce magnetic force
per unit of charge depending on velocity
B = F magnetic / q v
B = N/C m/s T
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F mag = B q v
 Magnetic Field produced by current
B = F magnetic/ I x L B = N/C/s m T
Uses of Magnetism
 Solenoids, speakers, doorbells,
galvanometers, motors and generators,
ignition coils, CAT scans and MRI…….
Electromagnetic Waves
 Electromagnetic Wave – transverse wave of
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electromagnetic radiation
Energy is stored in electric and magnetic fields
and transferred in the form electromagnetic
waves
Oscillating electric and magnetic fields
propagated perpendicular to one another
Produced by an exited electron (electric field)
returning to ground state
Quantized (Plank)
Photon (Einstein)
Dual Nature – Particle and Wave-like