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ELECTROMAGNETS
on
Activity Sheet GTE-12A
e
Objectives: To explore electric circuits in order to explain how they relate to magnetic
fields.
ENERGY Note: Are electricity and magnetism related?
Materials (per group)
1 box of paper clips
compass
2 D cell battery holders
2 D cell batteries (1.5 V)
magnet
switch
Activity 1: Exploring a Compass
1. Take the magnet and the compass. Hold them about 30 cm apart.
2. Slowly move the magnet closer to the compass. Record your observations. Repeat if
necessary.
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Activity 2: Circuits and Compasses
3. Construct a simple circuit using the provided materials. (Just 2 cells wired to a switch) Leave
the switch open.
4. Place the compass near the circuit. Record your observations in the left half of Figure 1,
“Compass Observations.” (Draw the compass needle.)
5. Close the switch. Record your observations in the right half of Figure 1, “Compass
Observations.” (Draw the compass needle.)
FIGURE 1
COMPASS OBSERVATIONS
OPEN
CLOSED
N
N
W
E
S
W
E
S
6. Explain the movement of the compass needle after the wire was connected to the circuit. Use
your observations and prior knowledge about the effects of magnets on compass needles to
support your answer.
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The observations you just made represent one of the biggest blunders in the history of
science. However, this blunder has revolutionized technology and enabled scientists to
develop devices that convert electrical energy into mechanical energy.
7. Read notate the passage, “Oersted’s Surprise.”
OERSTED’S SURPRISE
Many of the greatest scientific discoveries have been lucky accidents. Electromagnetism was one of
those. During a lecture in the year 1819, Hans Oersted had a compass sitting next to a wire. When
Oersted completed the circuit by connecting the wire to a battery, the direction that the needle was
pointing changed. This indicated that the electricity flowing through the wire had created a
magnetic field. When he stopped the flow of electricity, the compass needle returned to its original
position. Although most scientists are pleased by these unexpected discoveries, Hans Oersted was not.
His lecture that day was supposed to demonstrate that electricity and
Figure 1
magnetism have absolutely nothing to do with each other.
Solenoid
André Ampere followed up on this discovery and found that two
parallel wires carrying electric currents running the same direction
attracted each other. This observation led to the creation of a
solenoid or coil as shown in Figure 1. In the solenoid, the magnetic
field created by a loop of wire carrying an electric current joins
together with the magnetic fields from other coils of wire to create
more powerful magnetic force. This magnetic field only lasts as
long as the electric current is flowing through the coils of wire.
It has been found that the overall strength of the field could be
further amplified by inserting a ferrous (iron containing) core into the center of the wire loops. This
increased field strength occurs because the domains inside the metal core temporarily align with the
magnetic field produced by the currents flowing through the wire coils. The magnetic field from the
ferrous core joins with the magnetic field created by the wire loops surrounding the core. This
combination can be used to create very strong magnets that can be turned on or off instantly, called
electromagnets. Electromagnets can be used to lift heavy objects such as automobiles or scrap metal.
They are also used to support the weight of Mag-lev trains found in Europe and Asia.
8. Why does a compass needle move when it is placed next to an electrical circuit? Use
information from the reading to support your response.
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Homework: Electromagnets Lab – Pre-reading and Hypothesis