Making an Electromagnet
Recall that a piece of iron in a strong magnetic field becomes a magnet
itself. An electromagnet is a magnet made by placing a piece of iron
or steel inside a coil of wire. As long as the coil carries a current, the
metal acts as a magnet and
iron
coil
increases the magnetic field of
core
the coil. But when the current
is turned off, the magnetic
domains in the metal become
S
N
random again and the magnetic field disappears.
By increasing the number
of loops in the coil, you can
increase the strength of the electromagnet. Electromagnets exert a much
more powerful magnetic field than a coil of wire without a metal core.
They can also be much stronger than the strongest permanent magnets
made of metal alone. You can increase the field strength of an electromagnet by adding more coils or a stronger current. Some of the most
powerful magnets in the world are huge electromagnets that are used
in scientific instruments.
check your reading
How can you increase the strength of an electromagnet?
Electromagnets
How can you make an electromagnet?
SKILL FOCUS
Observing
PROCEDURE
1
Starting about 25 cm from one end of the wire, wrap the wire in tight coils
around the nail. The coils should cover the nail from the head almost to
the point.
2 Tape the two batteries together as shown. Tape one end of the wire to a free
battery terminal.
3 Touch the point of the nail to a paper clip and record your observations.
4 Connect the other end of the wire to the other battery terminal. Again touch
the point of the nail to a paper clip. Disconnect the wire from the battery.
Record your observations.
WHAT DO YOU THINK?
• What did you observe?
• Did you make an electromagnet? How do you know?
CHALLENGE Do you think the result would be different
if you used an aluminum nail instead of an iron nail? Why?
538 Unit 4: Electricity and Magnetism
MATERIALS
•
•
•
•
•
insulated wire
large iron nail
2 D cells
electrical tape
paper clip
TIME
20 minutes