Transcript PHY 231 Lecture 29 (Fall 2006)

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Physics 213
General Physics
Lecture 8
Last Meeting: Kirchhoff Rules, RC
Circuit
Today: Magnetism & Magnetic
Field
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Magnetic Resonance Imaging
(MRI)
Maglev Train
Examples of Other Magnetic Field Applications

Demo

Magnetic Materials, Magnets
 Dip Meter
 Attraction and Repulsion
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Demo: iron filings
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Magnetic Field Lines, sketch
A compass can be used to show the direction of
the magnetic field lines (a)
A sketch of the magnetic field lines (b)
Magnetic Field Lines, Similar to
Electric Dipole
Magnetic Dipole
Electric Dipole
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Earth’s Magnetic Field
The Earth’s magnetic
field resembles that
achieved by burying
a huge bar magnet
deep in the Earth’s
interior
A Few Typical B Values
Conventional laboratory magnets
25000 G or 2.5 T
Superconducting magnets
300000 G or 30 T
Earth’s magnetic field
0.5 G or 5 x 10-5 T
Crookes Tube
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Determining the Direction of
Force, the Right Hand Rule
Point your fingers in the
direction of v
Curl the fingers in the
direction of the magnetic
field, B
Your thumb points in the
direction of the force, F , on
a positive charge
If the charge is negative, the
force is opposite that
determined by the right hand
rule
Right Hand Rule Examples
F
.
v
F
-e
v
-e
B
B
Velocity out of
page.
Velocity into
page.
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Q3
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