Redirecting/stopping Magnetic Fields

Railguns use magnetic repulsion, but the rails themselves are not magnetic.

The basic principle is (more or less) that the rail completes an electric circuit, however the current creates opposing magnetic fields, which act on the projectile to propel it (right hand rule).

Compare this to a Gauss rifle which basically uses a series of electromagnets to accelerate a projectile (I don't remember off the top of my head whether the projectile has to be ferromagnetic or just conductive).

 

I'm familiar with diamagnetism and paramagnetism - in Chemistry we have a set of very sensitive balances that we use to measure the diamagnetic/paramagnetic properties of solid samples (not to mention to determine if the sample is diamagnetic or paramagnetic). This is useful to chemists because it can allow us to infer information about the elctronic structure of the analyte, which in turn can allow us to (among other things) determine between High spin and low spin configurations.

Addendum: All of which is beside the point that I was making, which is that Railguns rely on Lenz's force law, rather than the magnetic properties of the projectile, where as a gauss gun requires the use of a ferromagnetic projectile, and is dependent on the magnetic properties of the projectile.

 

Correct.
Paramagnetic elements are attracted to magnetic fields.
Diamagnetic elements are repelled by them.

The balance we use takes a small sample, measures its weight, applies a magnetic field of known strength and polarity, then remeasures its weight. The difference in weight is degree to which it is repelled or attracted by a magnetic field and the sign of the difference tells you whether or not the material is diamagnetic or paramagnetic. As I said, the magnitude and polarity of the difference can give you information about the electronic structure of the material, and differentiate between high spin and low spin configurations (because they have different numbers of unpaired electrons and respond to magnetic fields differently).

I for one would not be volunteering for any such ride.