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Magnetic Fields 2
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Un-magnetized domains are aligned in various directions
Magnetized domains are aligned in a N –S direction
N S
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If a bar magnet is broken, each piece has a N and S pole
A given pole cannot be separated from the other pole (there are no monopolar materials)
SN N S N S
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A permanent magnet can be destroyed by heating or vibration
Change in the kinetic energy of atoms, domains are misaligned
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A magnetic field ( ) is the region surrounding a magnet in which magnetic forces exist
Two kinds of magnetic force, attractive and repulsive
BB
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Like poles repel
Unlike poles attract
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Magnetic fields are vectors, have magnitude and direction
The direction of a magnetic field ( ) is defined as the same direction of the magnetic force exerted onto the north pole of a compass
B
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The direction in which the N-pole of a compass points indicates the direction of magnetic field.
Line of force - the path taken by the N-pole of a compass when free to move in a magnetic field
The number of lines of force through a region or space is called magnetic flux density
The density is proportional to magnetic field strength
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A – higher density of field lines, greater B, greater Fm
B – lower density of field lines, lesser B, lesser Fm
Greatest density of field lines is near the poles of a magnet
A
B
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Magnetic lines of force are continuous
The direction of a magnetic field line outside a magnet is N to S and inside is from S to N
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The Earth’s magnetic field is similar to a bar magnet
The field is the result of the fluid motion of iron within the earth’s core (read text for new theories)
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22° E of N in Alberta
Magnetic north in the northern hemisphere
South magnetic pole of the Earth’s magnetic field