Nigel, The collision of two oppositely charged particles can be far more energetic when they collide within a current than in isolation. How much more depends on the current strength/density and particles' location.
The particles borrow field momentum from the magnetic vector potential(A) the current collectively creates. For example, see - '(Section 213) Two kinds of momentum' The Feynman Lectures on Physics Vol. III Ch. 21 http://www.feynmanlectures.info/docroot/III_21.html If the two particles collide with nearly the same momentum (in the lab frame), suddenly they see an almost immediate drop in the magnetic vector potential which generates an additional huge electric field(E) gradient propelling the particles into each other, i.e., see Feynman's (Equation 21-16) E = -dA/dt As Feynman notes: "That electric field is enormous if the flux is changing rapidly, and it gives a force on the particle. The force is the charge times the electric field, and so during the build up of the flux the particle obtains a total impulse (that is, a change in mv) equal to −qA. In other words, if you suddenly turn on a vector potential at a charge, this charge immediately picks up an mv-momentum equal to −qA." If you are interested in how the vector potential stores momentum, sse- "Thoughts on the Magnetic Vector Potential" http://abacus.bates.edu/~msemon/thoughts.pdf The extra energy picked up by light particles like electrons and positrons will be far higher than by much heavier protons and nuclei. (Another different approach to calculating the extra energy is via the Darwin Hamiltonian/Lagrangian.) This effect is not very significant in chaotic plasmas, such as in a Farnworth fusor device since there is too much field cancellation due to random motion. It can be very large for plasma arc filaments, though. -- Lou Pagnucco Nigel Dyer (Sat, 15 Feb 2014) wrote: > I may be being stupid here, but if you have two charged particles > moving towards each other then can they not be thought of as generating > magnetic fields, and that these magnetic fields would form the basis of > an additional attraction alongside the column force. electric and > magnetic fields differ only in their frame of reference. > > I could well imagine that there are multiple ways of showing this
