Magnetism
A) Magnetism is a force that exists between moving charges
Moving charges always create magnetism
Natural Magnetism comes from - spinning ...
... electrons in atoms
Electric current -
Where there is electricity there is always
magnetism !!!!
B) Magnetic Fields - regions in space where a magnetic forces may be detected
Magnetism - David Colarusso
We will focus on fields around:
1) current carrying wire
2) permanent & electromagnets
3) Bar Magnets
Magnetic lines of force of a bar magnet shown by iron filings on paper:Magnet from Practical Physics, publ. 1914 by Macmillan and Company - copyright expired
(Actual magnetic fields contain many more lines of magnetism)
1. Magnetic flux lines - lines of magnetism in a magnetic field.
- magnetic field is not continuous.
Between each line of magnetism there exists ....
... no magnetic field
a) The needles of a compass line up perfectly with the flux lines
b) The arrows on a flux line show where the North Pole of a compass would point in that field.
Compass Arrows point
OUT of NORTH
INTO SOUTH
and back over
again to North
c) Magnetic force strongest at the ...
Poles ...
... where flux lines are closest.
Cutting Magnets ...
... each piece is a brand new magnet
How can magnets
attract non-magnets?
Directions: Slide the magnet on the right over to the metal on the left. (unmagnetized metal on left)
Certain metals contain magnetic regions called domains. They are randomly orientated.
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| The magnetic field in the bar magnet reorient the random magnet domains in the metal | |
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Ex) Which diagram best represents magnetic flux lines around a bar magnet?
d) Measuring the strength of a magnetic field
Put a wire with a known current into the field and measure the force on the wire