Download Magnets exert forces Magnets have two poles

Electricity and Magnetism
closely related
Intro to Magnetism
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Objectives/Syllabus Refs:
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6.3.1: State that moving charges give rise to
magnetic fields.
6.3.2: Draw magnetic field patterns due to
currents.
6.3.5: Define the magnitude and direction of a
magnetic field.
Magnets exert forces
 On
other magnets or iron
objects
 Over a distance
 Attractive or repulsive
Discovered relationship in 19th
century
 First magnetic rocks discovered 2000
years ago in “Magnesia”
 12th century Chinese used them to
make compasses and navigate
 Today many uses: electric motors
and generators
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Magnets have two
poles
 North
and South
 Can’t be isolated
 Opposites attract, like poles
repel
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Magnetic Fields (B)
 Represented
 Direction
by field lines
indicated by N compass
needle
 Direction
of force is tangent to that
point
 Magnitude
by concentration of lines
 Sims/Diffs
Sims/Diffs
w/ electric and
gravitational
Electric current and magnetic
field
 1820
Hans Christian Oersted
 Magnetic field is in a circle
around a current carrying wire
 RightRight-Hand Rule
 Grip
wire with right hand with
thumb in direction of conventional
current,
current, fingers will wrap in
direction of magnetic field.
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Moving electric charges
cause magnetism
 Electron
spin and revolution
 Cancelled
out in most
substances, not in iron
 Domains and magnets
 Currents
are electron motion =
magnetism
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