electric motor

This is an electric motor that can be made quite easily

adjust the positions of the switch and the coil until the motor goes on turning when you spin it. Reed switches damage easily and a partly-working switch will stop the motor working. If the motor is run without the capacitor the switch will arc in a very satisfactory way for a few moments and then stop working or even worse work only intermittently. The problem is minimised if only one battey is used but the motor works much better with more batteries. It works really well with neodymium magnets.
If the coil is made with a ferrite core it will work much better, although it can be made to work with a few turns of insulated wire round a nail. This is almost a short circuit. Because you are holding the coil you can feel if the wire overheats; you can also feel the attraction & repulsion of the magnets. Your other hand senses the influence of the magnets on the reed switch.

similar motor on youtube

homopolar motor

This is a much simpler motor, you need a neodymium magnet and a short length of copper wire

I have modified this design to try & make it so you don't have to bend the wire quite so precisely. I have added a coin made of some metal that sticks to magnets. I don't know what pennies are made of but it isn't copper. The coin goes in between the magnet and the battery to make it easier for the wires to brush against the bottom terminal. If you are lucky enough to have a neodymium magnet with a wider diameter than the battery then you don't need the penny, the magnet itself will act as the terminal. I have used a bit of drinking straw resting on the positive terminal to keep the bearing central. If you are using enamelled copper wire be sure to scrape off the enamelling where it touches the top terminal and where the legs brush against the penny.

It works even though the wire is quite unevenly bent. This is a detail of the top terminal

If the 'V' of the bent wire is too pointed it gets stuck between the bit of straw and the top of the battery. If you use a new battery you will need to secure the bit of straw with some blue-tack. Also beware of the wire jamming with a new battery because the penny can quickly get very hot. For some reason the penny seems to heat up rather than the wire. movie

fleming's left-hand rule
eddy currents
less money
flashlight battery made from pennies
link to another simple motor

electric motor made without a permanant magnet

This design, although quite complex can be made without a permanant magnet, however you do need some thin enamelled copper wire to make the coil (I used 0.3mm wire).

An armature made from about 2 inches of 3mm fence wire is intermittently drawn into a coil as the current is switched on & off. I made the coil by wrapping about 20ft of copper wire round a paper tube, the clearance between the armature & the tube should be as little as possible; making the coil is perhaps the most demanding part of making the motor.

The armature pulls on a piece of cotton which pulls the crank round: this method of hanging the cotton from the crank means the cotton can be easily removed, but it won't slip off of its own accord

The wire support structure is part of the circuit: it transmits electricity to the crank via the two bearings. One of the bearings supports the weight of the paper flywheel from below

while the other one counteracts the tendancy of the other end of the crank to lift

The circuit is completed by a pivoted length of wire which brushes against the end of the crank

the end is folded back on itself & half covered with sellotape. I found it was almost impossible to half-cover a bit of wire with sellotape, but it's quite easy to cover the bit of wire that doubles back. This breaks the circuit when the crank is on the way up.

I found I could make it work with 2 AA batteries, any more than this will make the coil overheat. I had to balance the paper flywheel quite carefully with little bits of blue-tack to compensate for the weight of the armature

movie on youtube
similar motor made from a hinge
Lenz's law

my email is davidvwilliamson@hotmail.com
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