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Electric and Magnetic Attraction Differences
Name: Julia
Status: educator
Grade: 4-5
Location: WI
Country: N/A
Date: 10/31/2005
Question:
If static electricity (i.e. a wool-rubbed balloon making
your hair stick up) attracts objects due to the negative charge being
built up, then why won't the negative pole of a magnet attract the same
objects?
Replies:
Dear Julia,
Magnets do not attract (or repel) stationary charges since the magnetic force
is quite different from the electric force, although it is closely related.
Stationary charges are not affected by magnetic fields. Moving charges
passing through a magnetic field do feel a force, but the force is
perpendicular to the magnetic field line. This is unlike the electric
force, which is parallel to the electric field lines. Since electric field
lines radiate from electric charges, the electric force will attract charges
toward (or away from) the charge producing the electric field.
Since magnetic field lines radiate from the poles of a magnet and the
magnetic force is perpendicular to the field lines (as well as perpendicular
to the velocity of the charge), a charge passing in front of a pole will
have its direction changed, but will not be attracted to or repelled from
the pole.
Best, Dick Plano, Professor of Physics emeritus, Rutgers University
Julia,
North and South poles of a magnet are not in any way electric. They are not
positive and negative charges of any sort.
Every atom is a tiny magnet. If you attach a coil of wire to a battery so
that electric current runs through the coil, the coil becomes magnetic (i.e.
an electromagnet). In the same way, the motion and spin of the particles
inside an atom cause the atom to be magnetized.
In a standard magnet, many of the atoms "face the same direction". Their
tiny magnetic fields work together to produce a large magnetic field.
Neither pole of a magnet is positive or negative. The poles just tell you
which way the atoms face.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
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Update: June 2012
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