system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:If a Rail Gun does not use propellant, why is there exhaust fire in the videos?

Rail guns give a projectile kinetic energy through electromagnetic propulsion, much like a monorail.  So why the big boomy looking stuff in the vids?
gpt
That's not fire, that's plasma.

A railgun, consists of two conductive rails, and a large bank of capacitors. The projectile is electrically conductive and sits between the two rails. When the railgun is fired, the capacitors are connected to the rails, and a very high current (around 1000000A) flows through the rails, creating a strong magnetic field which propels the projectile down the track.

This current is so high that it vaporizes parts of the conducting armature that carries the projectile - which creates the cloud of plasma that you see in the images.

Also, there's a number of anwers that say it sets the air on fire. Fire is a reaction between oxygen and *some other fuel* ; oxygen alone does not burn.