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# Magnetic Forces on Electric Currents

"A fact is a simple statement that everyone believes. It is innocent, unless found guilty. A hypothesis is a novel suggestion that no one wants to believe. It is guilty, until found effective"
Edward Teller

- An electric current is simply a collection of charges moving along a wire with velocity vd , known as the drift velocity. We have already seen that the drift velocity and current density are related by

> Considering the magnetic force on a single charge (e) we find
> Now the total force on a wire comprised of (nAl) charge carriers each with charge e is given by
> Defining a vector l along the wire in the same direction as J and using |JA| = i (electric current) we find for the total force on the wire
> Note that for a given current negative and positive charge carriers move in opposite directions. This leads to a force on the wire in the same direction (see above), whether the charge carriers are positive or negative.

When chemists die, they barium.

Dr. C. L. Davis
Physics Department
University of Louisville
email: c.l.davis@louisville.edu