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Re: More Wireless Power Transmission (fwd)
---------- 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