Chapter 24 Magnetic Fields. Magnet A substance that has polarity.
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Transcript of Chapter 24 Magnetic Fields. Magnet A substance that has polarity.
![Page 1: Chapter 24 Magnetic Fields. Magnet A substance that has polarity.](https://reader036.fdocuments.in/reader036/viewer/2022081515/56649ee85503460f94bfa2c6/html5/thumbnails/1.jpg)
Chapter 24Magnetic
Fields
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Magnet•A substance that
has polarity
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Polarity•Charge separation that results in one end being
positive & the other end being negative
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Magnets•The ends are called the north & south poles
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Magnets•North pole = (+)
•South pole = (-)
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Magnets•Opposite poles
attract & like poles repel
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Some metals can become temporary
magnets by bringing them close to a strong magnet
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Most Permanent magnets are made of ALNICO, an alloy
of Al, Ni, & Co
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Very strong, but expensive
permanent magnets are made of neodymium
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Magnetic Field•Space where
attractive & repulsive forces act
around a magnet
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Magnetic Field•Force fields similar
to gravitational & electric fields
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Magnetic Flux•The number of
field lines passing through a surface
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Field Strength•Magnetic field
strength is proportional to the flux per unit area
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A temporary magnet concentrates
magnetic field lines and is attracted to a permanent magnet
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A temporary magnet repels magnetic field lines and is repelled from a
permanent magnet
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Electromagnetism•Electric current
generates a magnetic field &
vice versa
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Hans Christian Oersted
•First to observe electromagnetic
properties
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Electromagnetism•Electric field lines
& magnetic field lines are
perpendicular
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First Right-Hand Rule
•Explain •(page 497)
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Passing a current through a wire wrapped around a piece of metal
generates a magnetic field
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Electromagnet•Magnet generated
by passing a current through a
coiled wire
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Second Right-Hand Rule•Explain
•(page 498)
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Magnetism at the atomic level•Results from
magnetic fields of electrons
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Domain•A group of about 1020 atoms acting
together electromagnetically
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Domain•Each domain acts like a dipole (polar
unit)
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Magnitism•Magnetism occurs when domains are
aligned
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Passing a current through a wire in a
magnetic field exerts a force
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Third Right-Hand Rule
•Explain•(page 503)
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Magnetic Induction (B)
•Strength of a magnetic field
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Magnetic Force•Proportional to
current, field strength, & length
of the wire
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Magnetic Force
F = BIL
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Magnetic Induction (B)
B = F/IL
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Magnetic Induction (B)Measured in
teslas (T)
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Tesla (T)
T = N/Am
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Galvanometer•Device used to
measure very small currents
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Galvanometer•Passing current through
a looped wire in a magnetic field creates a force causing the wire to rotate (page 505)
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Galvanometers•Use 3RHR to force a needle to move as
current passes through a MF
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Galvanometers•Can measure
currents as small as 10-6 A
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Galvanometers•Cannot rotate more
than 180o or more than 90o from parallel to B
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Electric Motors•Must be able to
spin 360o
•Explain (page 506)
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Electric Motor Force
F = nBIL
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F = forcen = # of loops
B = magnetic field strengthI = current
L = length of wire loop
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Force on a single charged particle
F = Bqv
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F = forceB = Field strength
q = chargev = velocity