Re: More Wireless Power Transmission (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 05 Oct 2007 08:09:36 -0700
From: Ed Phillips <evp@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: More Wireless Power Transmission (fwd)


Then inductance is what?

Jim"

	The formal definition which I learned in college is that inductance is "flux linkages per unit current".  I have a copy of "ELEMENTARY LESSONS IN ELECTRICITY & MAGNETISM" by Sylvanus Thompson which was published in 1894.  This was a period in which different units were first being given formal names like voltage [often called "pressure", even by Tesla at times] and current ["quantity"].  Here is what he has to say:

	"Let the symbol L be used to represent the total amount of cutting of lines [of magnetic field] when a current of 1 ampere is suddenly turned on or off in it.  This quantity L is called "the inductance" of the circuit.  It was formerly [sometime before 1894] called "the coefficient of self induction".  The unit of induction is called the henry and corresponds to a cutting of 10^9 magnetic lines when 1 ampere is turned on or off."

The point is that the magnitude of inductance determines such effects as the voltage induced in the coil by a given time rate of change or current or the time rate of current when a voltage is impressed upon it, but it is present whether or not such current or voltage is there or not.

Ed