Phys 4, Section
2
Feb 22, 2002
Magnetic Field of a Current Element
Amount of charge dQ in a small element dL of a wire with
crosssection A carrying a current I is given by dQ =
nqA dL where n is the free charge density. Putting this into
the standard equation for the magnetic field of a moving charge gives
For a very long wire carrying a current I, the field at a distance r
from the wire is given by
Force between Parallel Conductors
If the wires are each carrying currents I_{1} and I_{2}, then
setting up the Bfield from one wire and calculating the force that Bfield
exerts on the current in the second wire gives
Last modified on February 27, 2002
