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Any metal conductor such as aluminium or copper is a conductor because of the free electrons in such metals.

Plasma also has free electrons so I would like to know if you can repel plasma the same way as aluminium is repelled when near an AC electro magnet?

If so how come when I spin a magnet near my plasma globe there is no noticeable reaction compared to an aluminium can?

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  • $\begingroup$ I'm not sure that your 'plasma globe' actually contains what physicists understand under plasma $\endgroup$
    – Danu
    Jun 1 '14 at 13:05
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So a plasma globe contains noble gases at roughly atmospheric pressure. The centre of the globe has an electrode contained within a glass bulb (to contain the gases which are otherwise quite good at finding gaps due to their atomic nature). This central electrode is at high voltage (2-5 kV) and oscillates at high frequency (~35 kHz). This capacitively couples to the gas and leads to the plasma and avoids the outer glass envelope from charging up to high voltage. As a consequence of the oscillating electric field, the electrons in the plasma are themselves oscillating and so their velocity oscillates.

The lorentz force on each electron due to the magnetic field is dependent on the vector velocity of the electron, , $\underline{\mathbf{F}}=Bq\underline{\mathbf{v}}$, and so reverses direction in tandem with the velocity of the electrons. Because this reversal is happening at ~35 kHz (reversal every ~30 $\mu s$) you don't see any deviations - you just can't see things that happen that fast!

Magnetic fields are used to control plasma, but they rely on a net flow of charge in one direction or another so that the lorentz force is constant/not oscillating. That's why current fusion reactors are donut shaped, so the plasma (and associated electrons) circulate around and around through the static magnetic field.

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