Topband: Back to the basics with coils

Herb Schoenbohm herbs at
Wed Apr 27 06:15:43 PDT 2011

On 4/27/2011 7:36 AM, Gedking at wrote:
> Hmmm what is the instantaneous current when the voltage is applied and 
> what is it when it is shorted out???
> In a message dated 4/26/2011 10:49:37 P.M. Eastern Daylight Time, 
> herbs at writes:
>     Long before we were using RF to communicate very far Tesla had it all
>     right there......
>     Nikola Tesla explains that a standard coil of 1000 turns with a
>     potential of 100 volts across it will have a difference of 0.1 volt
>     between turns. A similar BIFILAR coil will have a potential of 50
>     volts
>     between turns.
>     In that the stored energy is a function of the square of the voltages
>     the energy in the BIFILAR will be ... 50 squared / .1 squared =
>     2500 /
>     .01 = 250,000 times greater than the standard coil
>     ------------------------------------------------------------------------
>     "Bifilar wound coils are used in the system because a bifilar
>     wound coil
>     maximizes the voltage difference between its turns, the current is
>     then
>     minimized."
>     ------------------------------------------------------------------------
>     "United States Patent Number 512,340 - COIL FOR ELECTROMAGNETS -
>     Nikola
>     Tesla, Inventor

In Tesla's own words on the coil patent application Jan 9, 1894:

*"I have found that in every coil there exists a certain relationship 
between its self inductance and capacity that permits a current of given 
frequency to pass through it with no other opposition that that of the 
ohmic resistance, or,in other words, as though it possessed no self 

*"In electric apparatus and systems in which alternating currents are 
employed the self induction of the coil and conductors may, and in fact, 
in many cases does operate disadvantagely by giving rise to false 
currents which often
reduce what is known as the commercial efficiency of the apparatus 
composing the system or operate detrimentally in other respects."*

Tesla goes on to points out that the detrimental effects can be 
mitigated by the use of "condensers."

*"My present invention has for its object to avoid the employment of 
condensors which are expensive, cumbersome, and difficult to maintain in 
perfect conditions, and so to construct coils themselves as to 
accomplish the same ultimate object." * (In over 100 years with 
condensers capable of high voltage and high current not much has changed 

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