BACKGROUND:
An electromagnet is a magnet that
employs electric currents to generate its magnetic field. In 1825, W.
Sturgeon described an electromagnet that allowed a 7 oz. iron bar to
pick up a 9 pound iron mass. When the electrical connection was broken,
the weight immediately fell. In 1829, H.C. Oersted discovered that an
electric current could turn a magnetized needle. Also in that year,
D.F.J. Arago and Sir Humphry Davy picked up iron filings by an
electrified wire on steel needles. This however, was not an
electromagnet.
Electromagnets are temporary magnets
that can be turned on and off just by removing one of the connections to
a battery. They can be made very strong by wrapping more coils around
the electromagnet. They are found in doorbells, door chimes, telephone
receivers, telegraphs, relays, loudspeakers, electric clocks, fans,
refrigerators, washing machines, generators, circuit breakers, and many
other electrical items.
PROCEDURE:
- This experiment shows students
that a more powerful magnet can be made by increasing the number of
coils around the bar while still using the same energy source (in this
case a total of 3 volts).
- Follow the directions on the
worksheet. Electromagnets can concentrate "energy" to make a
powerful magnet. These electromagnets are temporary. You may want to
extend this lab by joining two battery packs (a total of 6 volts). The
electromagnet will also get stronger. The number of coils and the
original voltage can create different electromagnet strengths.
- Make sure the insulation on the
ends of the wires is scraped off. The answers to the lab sheet are
dependant on how the students do the activity. Make sure the coils on
the electromagnet are wound tightly. The wire must have contact with the
nail.
- ANSWERS:
NOTE: When the students make an electromagnet in
this fashion, the wire will become very warm.
1. The number of paperclips will depend on how
tight the coils are and the type of paperclips.
2. The paperclips
fall.
3. More than in number 1.
4. No.
5. More than 3.
6. There should
be a little magnetism left.
7. Maybe 1 for a short period of time.
CONCLUSIONS: The force is stronger.
