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Any source of magnetism such as a magnet
or electromagnet is surrounded by a magnetic field.
Information about this field can be retrieved from
various devices. A compass can detect a magnetic field.
The shape of the magnetic field can be demonstrated with
iron filings. A gaussmeter will detect a field and
indicate its strength, measured in gauss units.
Questions you may have include:
A compass is simply a thin magnet or
magnetized iron needle balanced on a pivot. It can be
used to detect small magnetic fields. The needle will
rotate to point toward the opposite pole of a magnet. It
can be very sensitive to small magnetic fields.
When you bring a compass near an item
suspected of being magnetized or having a magnetic
field, the compass will turn and point toward the
appropriate pole of the object.
Compass needle attracted to magnet's N
pole
A famous experiment showed that a wire
with DC electric current running through it created a
magnetic field. When the electricity was turned on, a
nearby compass moved to indicate a magnetic field was
present.
The compass was used to discover that
the Earth is a huge magnet. The North-seeking pole of
the compass needle will always point toward the Earth's
North magnetic pole.
By spreading fine iron filings or dust
on a piece of paper laid on top of a magnet, you can see
the outline of the magnetic lines of force or the
magnetic field. The picture below
Iron filings and compasses show the
shape and direction of the magnetic field
This experiment also shows that
magnetism will act through many materials, such as
paper. Would the experiment work if a sheet of iron were
used to sprinkle the filings? What about aluminum foil?
A gaussmeter is used to measure the
strength of a magnetic field. They use a electronic chip
called a Hall effect device, which gives off a tiny
electrical current when exposed to a magnetic field. The
current is amplified with electronic circuitry and a
meter shows the number of gauss (the units of magnetic
field strength).
You can detect a magnetic field with a
compass, iron filings, or a gaussmeter. The strength of
a magnetic field is measured in gauss units. |
