Practical Guige to Free Energy Devices

thin layers of iron which are insulated from each other, then it can only handle low frequencies. You can forget
about trying to pass 10,000 cycles per second (“Hz”) through the coil as the core just can’t change it’s magnetic
poles fast enough to cope with that frequency. A core of that type is ok for the very low 50 Hz or 60 Hz
frequencies used for mains power, which are kept that low so that electric motors can use it.
For higher frequencies, ferrite can be used for a core and that is why some portable radios use ferrite-rod aerials,
which are a bar of ferrite with a coil wound on it. For higher frequencies (or higher efficiencies) iron dust
encapsulated in epoxy resin is used. An alternative is to not use any core material and that is usually referred to
as an “air-core” coil. These are not limited in frequency by the core but they have a very much lower inductance
for any given number of turns. The efficiency of the coil is called it’s “Q” (for “Quality”) and the higher the Q factor,
the better. The resistance of the wire lowers the Q factor.
A coil has inductance, and resistance caused by the wire, and capacitance caused by the turns being near each
other. However, having said that, the inductance is normally so much bigger than the other two components that
we tend to ignore the other two. Something which may not be immediately obvious is that the impedance to AC
current flow through the coil depends on how fast the voltage is changing. If the AC voltage applied to a coil
completes one cycle every ten seconds, then the impedance will be much lower than if the voltage cycles a million
times per second.
If you had to guess, you would think that the impedance would increase steadily as the AC frequency increased.
In other words, a straight-line graph type of change. That is not the case. Due to a feature called resonance,
there is one particular frequency at which the impedance of the coil increases massively. This is used in the
tuning method for AM radio receivers. In the very early days when electronic components were hard to come by,
variable coils were sometimes used for tuning. We still have variable coils today, generally for handling large
currents rather than radio signals, and we call them “rheostats” and some look like this:
These have a coil of wire wound around a hollow former and a slider can be pushed along a bar, connecting the
slider to different winds in the coil depending on it’s position along the supporting bar. The terminal connections
are then made to the slider and to one end of the coil. The position of the slider effectively changes the number of
turns of wire in the part of the coil which is being used in the circuit. Changing the number of turns in the coil,
changes the resonant frequency of that coil. AC current finds it very, very hard to get through a coil which has the
same resonant frequency as the AC current frequency. Because of this, it can be used as a radio signal tuner:
If the coil’s resonant frequency is changed to match that of a local radio station by sliding the contact along the
coil, then that particular AC signal frequency from the radio transmitter finds it almost impossible to get through
the coil and so it (and only it) diverts through the diode and headphones as it flows from the aerial wire to the
earth wire and the radio station is heard in the headphones. If there are other radio signals coming down the
aerial wire, then, because they are not at the resonant frequency of the coil, they flow freely through the coil and
don’t go through the headphones.
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