# Coiling myths

• To: tesla@xxxxxxxxxx
• Subject: Coiling myths
• From: "Tesla list" <tesla@xxxxxxxxxx>
• Date: Mon, 04 Apr 2005 12:55:16 -0600
• Delivered-to: testla@pupman.com
• Delivered-to: tesla@pupman.com
• Old-return-path: <teslalist@twfpowerelectronics.com>
• Resent-date: Mon, 4 Apr 2005 12:57:56 -0600 (MDT)
• Resent-from: tesla@xxxxxxxxxx
• Resent-message-id: <WjsySB.A.RXH.y4YUCB@poodle>
• Resent-sender: tesla-request@xxxxxxxxxx

`Original poster: Paul Nicholson <paul@xxxxxxxxxxxxxxxxxxx>`

```While I'm in the mood for summarising things, I thought I'd list
some of the theoretical myths that seem to keep cropping up in
Tesla coiling:-```

```* Myth: Signals travel through a coil as if they were moving at
light speed through the wire.```

```(They don't.  The effective velocity 'along the wire' of a solenoid
is given to within a few percent by ln(h/d)*0.39 + 1.19 times c.)```

```* Myth: Lumped operation is a different thing from distributed
operation.```

```(These are just two levels of detail in the mathematical modelling
of coil resonance.)```

```* Myth: Voltage magnification is much higher than the turns ratio
of secondary to primary, attributed to 'resonant rise'.```

```(The voltage ratio is rather less than the turns ratio due to the
limited coupling between the two coils.)```

```* Myth: Current in the wire offers a different mechanism for energy
transfer to the E and H fields.```

```(It doesn't.  Fields and currents are bound together, and a given
energy flow (along a coil, say) can be described equivalently
using either set of terms.)```

```* Myth: The low frequency inductance, Ldc, as measured by an LCR
meter or estimated by Wheeler, is the effective resonating
inductance.```

```(It isn't. It doesn't correctly represent either the stored energy or
the ratio of top volts to base current, because it doesn't allow for
the non-uniform current.)```

```* Myth: The bulk capacitance of the coil, Cdc, (measured at uniform
voltage by an LCR meter) is the effective resonating
capacitance.```

```(It isn't.  It has the same defects as Ldc because it doesn't allow
for the non-uniform voltage in the resonating coil.)```

```* Myth: High Q factor is important for secondary coils fired from an
initial charged primary cap.```

```(Only a modest Q is required.  Output voltage is not proportional to
Q as some suggest, but is limited by energy conservation.)```

I've only listed the myths that I feel confident to discuss and
refute. Perhaps others can add to the list from their fields of
expertise? Let's not bother with the numerous myths about
Tesla Himself, nor the inane core beliefs of the many modern techno-
superstitions.
--
Paul Nicholson
--