A Tabletop Demonstration Railgun

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Railguns operate according to the principle that when a current is at right angles to a magnetic field, a force is produced at a right angle to the current and the magnetic field.

Figure 1: F = I l x B

A railgun consists of two rails with a projectile in between. A current is passed down one rail, through the projectile, and back through the other rail. A magnetic field is set up around the currents in the rails, in the same way that a magnetic field is set up around any wire carrying a current.

Figure 2 : Induced Magnetic Field from a Current Carrying Wire

The current in the projectile is at a right angle to the magnetic field between the rails, which sets up a force acting to push the projectile away from the current source.

Figure 3 : Force Acting on Projectile