Friday 29 August 2014

electromagnetism - How does a "coilgun" work?


I was wondering how that so-called "coilgun" works, I know what it does but I was wondering how it works under-the-hood and eventually how to make a basic one ? Also, how much energy would be required ?



Answer



A coilgun is a series of coils that are successively energized as a conductive projectile made from magnetic material passes by them.


coilgun


Each stage acts on similar principles to those of a solenoid. Current loops induce magnetic flux through their center:

http://en.wikipedia.org/wiki/File:VFPt_Solenoid_correct2.svg


As the conductive projectile approaches the air-core current loops, two things happen: the loop inductance increases and the projectile becomes magnetized. The magnetized projectile is then attracted to the loop magnetic field, accelerating towards it. As it approaches, inductance increases, completing a positive feedback loop such that the pull on the projectile and magnetic field created by the loops increase.
alt text


This process reaches a peak when the projectile is completely enclosed by the coil, where further travel decreases the loop's inductance. At this point, current through the loop is abruptly turned off so the projectile won't be slowed down by its continued attraction to the coil's magnetic field.
alt text alt text WikiPedia gif


These are the basic physics principles by which a coil gun operates, which appears to be what you are interested in. There are many practical implementations.


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