THROUGHOUT history, humans have found ways to make their lives easier. Arguably, the machine that has most eased the burden of work for humans is the electric motor – a device that transforms electricity into motion.
You can find these at the heart of every washing machine, dishwasher, lawn mower, vacuum cleaner, food processor and in countless other household appliances and industrial machines. I imagine quite a few readers of this magazine will have, like me, delighted in extracting the motor from a broken toy or gadget and making it spin by connecting a battery to its terminals.
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However, I suspect fewer of you will know just how easy it is to show a child how to construct their own electric motor from bits and pieces that you probably have lying around the house.
Begin with a piece of copper wire. If your wire is insulated, strip at least 1 centimetre of insulation from each end. Then attach the flat head of a screw to one of the flat sides of a neodymium magnet.
Hold a battery up with one hand and touch the tip of the screw to the bottom of it. You should find that, when you let go, the screw will remain attached and hang down from the battery. If you can’t get this to work, you probably need a stronger magnet, or a lighter one.
Using a finger from the same hand with which you are holding the battery, hold one end of the wire so that it lies flat against the top of the battery.
Lightly touch the other end of the wire to the side of the magnet, and you should find the screw and magnet start spinning. Please take care when doing this – the wire will get hot if you leave it there for too long, so don’t keep it in contact with the magnet for more than a few seconds at a time.
As well as being utterly delightful, this simple electric motor illustrates a key aspect of the natural world that comes as a surprise to many children: electricity and magnetism are actually just two sides of the same phenomenon, electromagnetism.
Touching one end of the wire to the top of the battery and the other end to the magnet completes an electric circuit, allowing a current to flow through the wire, the magnet, the screw and the battery. An electric current such as this will always generate a magnetic field around itself.
A simple explanation of why the magnet spins is that, just as two permanent magnets in the same vicinity will exert a pull or push on each other, the magnetic field of the neodymium magnet interacts with the magnetic field of the current that flows through it, and does so in such a way that the magnet is made to spin.
Once you have got this to function, try asking the child you are working with how they could make the motor spin faster, or how they could make it spin in the opposite direction.
What you need
An AA, AAA or C battery
One or more neodymium magnets, ideally disc-shaped
A flat-headed metal screw, at least 2 cm long (make sure that it sticks to the magnet)
A piece of copper wire, around 15 cm long (insulated will do)
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Alom Shaha is a physics teacherÌýat a comprehensive school, and author of books including Mr Shaha’s Marvellous Machines. FollowÌýhim @alomshaha
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