An electromagnetic linear accelerator consists of one or more coils in the configuration of a LINEAR SYNCHRONOUS ELECTRIC MOTOR which accelerate a magnetic projectile to high velocity

The name Gauss gun is sometimes used for such devices in reference to Carl Friedrich Gauss, who formulated mathematical descriptions of the magnetic effect used by magnetic accelerators. The first such operational accelerator was developed and patented by the Norwegian physicist Kristian Birkeland

We know when current flows through an electromagnetic coil, a magnetic field is produced in its neighbourhood. Here such a coil is made to carry a very high current. This produces a very large magnetic field thus pulling a projectile towards it’s centre. The field is designed to shut off when the projectile is at the centre of the coil.