Unlike the electric
field, the magnetic field does not vanish in conductors.
Inside a conductor through which current flows,
there is some nonzero magnetic field. This is well
seen in Figure 1, which shows the magnetic field of a single
wire with uniform current distribution.
Similarly to the uniformly
charged cylinder and its electric field, the magnetic
field in a cylinder with uniform current density
increases linearly with the radial distance from
the center of the wire, i.e., . Once the observation
point crosses over to free space, the field strength
starts to decrease as —same as the
field of an infinitely long wire with current.
This behavior is illustrated in Figure 2.
Figure
3 shows the magnetic field in a coaxial-type
line with rather thick inner wire and shield.
Observe the behavior of the field magnitude both
in the inner wire, where it increases linearly,
and the outer shield, where it decreases linearly.
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Figures (click
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Figure 1 |
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Figure 2 |
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Figure 3 |
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