Cool Your School – Electricity Lab
Magnet, Coil, and Meter: Generating
Electricity
Outcomes:
1. Understand that electricity is not a source of energy, but a means of
transporting energy.
2. Understand that electrical current is generated by a changing magnetic
field in a coil of electrically conducting wire.
3. Understand the difference between direct current (DC) and alternating
current (AC).
Chabot Space & Science Center
1 | Page
Cool Your School – Electricity Lab
Materials:



Strong magnet (that will fit inside the wire coil tube)
Coil of electrical wire wrapped around a tube (the wire must be
insulated, not bare metal; coated “magnet wire” works very well)
Multimeter or ammeter to measure electrical current
What To Do:
1. Slide the magnet through the wire coil, in one direction, and use an
ammeter to observe the strength and sign (positive or negative) of the
electrical current produced.
What was the maximum current generated?
What direction did the current flow? (Did the ammeter show a positive
or a negative current?) In other words, what was the polarity of the
current, positive or negative?
2. Slide the magnet in the other direction through the wire coil.
What were the strength and polarity of the current this time?
3. Slide the magnet up and down repeatedly through the wire coil.
How does the electrical current behave when the magnet is repeatedly
moved up and down the coil?
Questions:
1. In this experiment, what is the source of the energy of the electrical
current you are generating?
2. How is the strength of electrical current affected by the speed that you
move the magnet through the wire coil?
3. Is there any difference in the behavior of the electrical current when
you move the wire coil instead of the magnet?
4. You have probably heard of “AC” and “DC” electricity. Do you know
what they stand for?
5. In this experiment, did you generate AC or DC electricity?
Further Experimentation:
With some spare wire and a toilet paper role, build your own electric
generator:
Chabot Space & Science Center
2 | Page
Cool Your School – Electricity Lab
1. First with only 10 turns of wire in the coil
2. Second, with 100 turns of wire in the coil
3. For each of these coils, hook up the wire ends to the meter and use
the magnet stack to generate some electrical current.
Questions:
1. What did you discover? How much current could you generate with ten
winds in the coil? How about a hundred?
2. What do you think is happening?
What’s Going On?
Moving a magnet through a coil of wire--or moving a coil of wire by a
magnet--induces electrical current in the wire. The direction that the current
flows through the wire depends on the relative direction of motion between
the magnet and the wire coil.
The strength of the electrical current depends on: 1) the strength of the
magnet, 2) the number of wraps of wire in the coil, and 3) how quickly the
magnet and coil move past each other.
The more wraps of wire the coil is made from, the more electrical current is
generated. If you think of each turn of wire in the coil as a single,
independent loop, or ring, each of which will have electrical current induced
by the passing magnet, then you can understand how a bunch of rings
together produce more current. A coil of wire is like a stack of wire rings
joined together.
Electrical current flowing continuously in one direction through a wire is
called “direct current,” or DC. We get DC directly from devices like batteries
and solar cells.
Electrical current flowing alternately back and forth through a wire is called
alternating current, or AC. Most of California’s electrical production comes
from power plants that produce AC by driving electric turbines, which consist
of huge magnets and coils of electrical wire. A hydroelectric plant uses
water pressure to drive the turbines, a geothermal plant uses steam
generated from Earth’s internal heat to drive the turbines, and a coal power
plant burns coal to produce steam to drive the turbines.
Chabot Space & Science Center
3 | Page
Cool Your School – Electricity Lab
Electricity is not a primary source of energy, but a convenient way to
transport energy from place to place. The actual sources of energy used to
generate the electricity are the coal, natural gas, geothermal heat, sunlight,
wind, and potential energy of water contained by dams that drive the
turbines.
The frequency with which our AC electricity alternates, back and forth, is 60
times per second—also called 60 Hertz (Hz). In this experiment, if you could
move the magnet up and down the coil of wire 60 times per second, you
would produce the same frequency of AC…. 60 Hz is just a standard number
that was decided upon for our AC power. In Europe, the standard is 50 Hz.
Chabot Space & Science Center
4 | Page
Cool Your School – Electricity Lab
Magnet and Coil Worksheets
With Wire Coil Provided in Experiment
Magnet moved through coil in one direction:
Maximum current ____________
Polarity(+/-) ______________
Magnet moved through coil in opposite direction:
Maximum current ____________
Polarity(+/-) ______________
Magnet moved up and down coil repeatedly:
Would the polarity of the current generated be better described by
the word “direct” or “alternating”?
With Wire Coils that You Made
Coil with 10 turns of wire:
Maximum current _____________
Coil with 100 turns of wire:
Maximum current _____________
Chabot Space & Science Center
5 | Page