Magnetic Linear Accelerator
This experiment is a simple way of demonstrating the distribution of the field inside a solenoid and how it effects ferrous metal objects.
This experiment simply consists of a plastic or cardboard tube with a coil of wire wrapped around one end. The coil can be powered by a set of standard batteries. the more batteries used the more powerful the magnetic field will be.
The tube used to for the coil around should be quite narrow. The case of a pen such as a biro is ideal. You can try using different sized batteries and different numbers of turns on the coil to produce different strength fields.
When a metal object is placed part way into the coil it is ready for firing. The metal should be ferrous (sticks to a magnet) and quite small. A metal rod of about 2 - 3mm wide and 10 - 20mm long is best. Something like a small nail or a screw with the head cut off should work fine. If a small rod magnet is used, it will work much better but make sure it's inserted the right way around, or it could backfire.
To fire the coil gun you simply tap the switch. If you press it for too long, the projectile will either stop in the middle or come back out the wrong end. You can practice different methods and different coil and battery sizes to see what results you get. An alternative firing method would be to use a circuit such as the PWM-OCX which can give repeated pulses or a time you can set youself.
For higher speed projectiles, it is possible to use multiple coils and fire them in sequence so that each one will futher accelerate the projectile. Each succesive pulse must be shorter than the previous one due to the projectile spending less time in the acceleration region. If the pulses were too long, they would drag the projectile back, slowing it down. Our 3 channel time delay generator could be used for controling the pulse timing to a transistor on each coil.