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Q & A: current density in London equation

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Most recent answer: 10/02/2012
Q:
why in London equation current density Js= -eNsVs where Ns, is charge density per unit volume and Vs, is velocities of super-fluid electrons in superconductor
- Dr. B.S. Rawat (age 34)
Dehradun, Uttarakhand, India
A:
That equation is probably the simplest part of the London equations. It simply says that the current density is the product of the density of charge carriers times the charge per carrier times their average velocity. That's basically true by definition of current.

The more challenging part of the London equations relates this current density to the magnetic field. There's a nice discussion of that question on Wikipedia.

Mike W.

(published on 10/02/2012)

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