sci.physics.electromag

Szczepan Bia=B3ek wrote:
>
> The above are commonly known. The hydraulic analogy is good enough for
> steady currents. But for oscillating no. To adopt the hydraulic equations
> for oscillating currents the displacement current was added. At that time
> "gas equations" did not exist.

Note that no less an authority than Maxwell points out (Treatise on
Electricity and Magnetism Chapter IV) That these analogies ESPECIALLY
the hydraulic one is actually NOT correct or "good enough". His
reasoning was that in the hydraulic case (and to a lesser degree in
the "gas" case) the failure has to do with the fact that the observed
actions in hydraulics are INDEPENDENT of the shape of the hose. In an
electric wire, induction for example, is VERY dependent upon the wire
shape or even if a piece of iron is nearby. Maxwell therefore
correctly concludes that a model for electric current in a wire is NOT
the hydraulic one and must be some kind of FIELD model with energy and
effects arising in the space OUTSIDE the wires!

Benj