Warning: This activity requires using a sharp blade or a lighter. Younger scientists should ask for an adult’s help with the first part of the activity. Neodymium magnets are extremely strong – take care not to pinch your skin between them.
You will need
• 25cm copper wire 
• Blade (if the wire is insulated)
• Lighter (if the wire is not insulated)
• AA battery
• 2 small neodymium magnets (about the same diameter as the battery)
• Pliers
What to do
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Straighten the 25cm of copper wire.
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If the wire is coated in an insulating plastic, carefully use the blade to remove it.
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If the wire is uninsulated, it might have a protective coating on its surface.
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This can be removed by carefully passing the wire through a flame. Beware – heating the wire makes it hot, so let it cool before touching it.
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Bend the wire into a love heart shape, where the ends meet towards the bottom of the heart.
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Place both magnets on the ‘–’ end of the battery and stand it upright on a table top.
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Balance the inside of the top ‘V’ part of the love-heart on the ‘+’ end of the battery.
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Bend the wire so the bottom of the heart sits either side of the magnets, lightly touching them.
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Bend the ends of the wire so they are parallel to the table’s surface and pointing in opposite directions.
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To set the mechanism spinning, it may need a slight nudge in one direction.
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If nothing happens, adjust the ends of the wire so they are close to the magnets but not quite touching.
What’s happening?
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The chemicals within a battery create a difference in voltage between the ‘+’ and the ‘–’ ends.
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But, for electricity to flow it needs something to flow through, called a ‘conductor’.
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Copper conducts rather easily, however electricity needs to get into the wire.
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Most wires are insulated for protection.
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Removing the insulation allows electricity to pass from one end of the battery, through the wire, to the other end.
Why does the wire spin?
Electricity is essentially a moving charge.
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This movement is due to a force called ‘electromagnetism’, which is also responsible for most chemical reactions, light and radiation, magnets, and also for making it impossible for you to walk through a solid wall.
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Whenever electricity flows, it creates a weak magnetic field around it.
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This means there is a weak magnetic field surrounding the copper wire, which ‘bumps’ into the magnetic field surrounding the magnets on the bottom of the battery.
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These two fields push against each other. As the magnets are harder to move than the wire, the wire spins freely, and will continue to do so until the battery can’t produce any more electricity.
Applications
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The pushing of the magnetic fields is called the ‘Lorentz Force’.
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It is used in a wide number of situations, such as in electric motors, generators, loud speakers and an accelerator called a ‘rail gun’.
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In a rail gun, two rails – like those of a train track – conduct electricity.
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To get electricity flowing between them, a piece of metal is used to form a full circuit.
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This metal is free to slide up and down the rails, and forms the projectile.
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As the current in the projectile creates an electromagnetic force which pushes against the force produced by the rails, it starts to accelerate.
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Rail guns can produce some fairly impressive speeds, and have even been suggested as a way to fire objects from low-gravity bodies in space.
You can view this experiment through youtube: http://www.youtube.com/watch?v=1ScLcjC81H4
Try another Science by Email activity using electromagnetism http://www.csiro.au/helix/sciencemail/activities/doorbell.html
More information
Variations on the homopolar motor ==> http://dangerouslyfun.com/homopolar-motor
Rail guns ==> http://science.howstuffworks.com/rail-gun1.htm
© CSIRO
Article generously contributed by CSIRO
Check out other activities for Kids by CSIRO:
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