magnetism the shadow of electricity. magnetic force magnets apply forces to each other. opposite...
TRANSCRIPT
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Magnetism
The shadow of electricity
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Magnetic Force
Magnets apply forces to each other.
Opposite poles attract, like poles repel.
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CPS Question
The magnitude of the force between magnetic poles
A. is the same at all distances.
B. becomes stronger as the poles come closer.
C. becomes weaker as the poles come closer.
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Magnetic Field Lines
Field lines point from North to South pole.
Conventions as with electric field lines.
strong field where lines are close together
direction is direction of force on a north pole
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Group Work
1. What happens to a dipole magnet in a uniform magnetic field?
B
N
S
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Naming the polesN = north-seeking
Earth’s north pole is a south pole!
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Current Creates Magnetism
An electric current creates a magnetic field.
Look, Ma! No poles!
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Vector Direction Conventions
Up Down
In Out
RightLeft
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Poll Question
If a wire in front of you carries a current from left to right, what is the direction of the resulting magnetic field where you are?
I
A. B. C.
D. E. F.
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Board Work
An electric current creates a magnetic field whose lines circle right-handed around it. Draw lines for the magnetic field created by a ring of current.
I
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Magnetic Field of Current Ring
Source: Griffith, The Physics of Everyday Phenomena
N
S
dipole field
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Solenoid Magnetic Field
Source: Griffith, The Physics of Everyday Phenomena
N S
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Electrons are Magnets!
spin
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Electrons are Magnets!
current
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Electrons are Magnets!
magnetic field
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Electrons are Magnets!
N
S
magnetic dipole
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Types of Magnets
• Electromagnets– currents travel through conducting coils
• Permanent Magnets– materials whose electrons have aligned spins
or orbits
Moving charges create the fields!