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Electricity and Magnetism
 
Aim: to make a Simple D.C. Electric Motor
See D.C. Electric Motor
 
The idea here is to show how the simplest type of d.c. motor works by constructing one from readily available bit 'n' pieces... be warned, it doesn't do anything useful, just spins round, quite fast if you're careful (and lucky!).
 
Bits 'n' Pieces Needed Tools Needed
   
1 wine bottle cork* (4cm long) scissors
2 nails (1mm 25mm) wire cutters/strippers
2 flat magnets  
Insulated copper wire (about 0.6mm diameter)  
1 piece of cardboard  
"Scotch" tape  
paper clips  
 
*It's easier to use a new cork (that is, one which does not come from a bottle of wine!)
 
Obviously there is some flexibility in the choice of some of these parts but be aware of two points:
1. the dimensions of the cardboard support are given assuming a cork about 4cm long and standard wine bottle diameter (whatever that is!)
2. the wire should be pretty close to 0.6mm diameter; thicker wire makes it difficult to get enough windings round the cork and thinner wire tends not to be rigid enough to make the brushes/commutator.
 
Start by cutting out and folding a piece of cardboard to make the frame of the motor as shown here.
 
Cut and fold the cardboard so that it looks like this (held in this position by the paper clips)
 
Strip about 2cm of insulation off the ends of two pieces of wire and thread them through the holes to make the brushes of the motor.
Push the nails into the cork, making sure they are in the centre.
Make a coil around the cork as shown below, leaving about 1cm of the ends of the coil uninsulated.
Place the coil in position in the cardboard frame and add the magnets.
To help make a good contact between the brushes and the ends of the coil, start with the brushes more or less touching each other so that they are forced apart when the coil is put in place, as shown below.
Here are a couple of photos of one version of the motor.
   
The complete motor (in all its cardboard glory)  
Click photo to see the motor running  
 
Close-up view of brushes
 
Connect to a d.c. supply of about 6V and watch it spin around at thousands, (well, ok, hundreds, ok maybe tens) of revolutions per second!
 
PS
The power supply must be capable of supplying a fairly high current... I found it worked well with a p.s. limited at 10A.
If it doesn't spin:
- you might need to give it a push to start it (you can probably see why this is the case...)
- check that the magnets are attracting each other not repelling
- fiddle about with the brushes to make sure here is a good contact between them and the ends of the coil
- that's about it, I think...
 
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