Help on how a Tesla coil excites a neon bulb / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

Help on how a Tesla coil excites a neon bulb

1 2 3 next

Move Thread

LAN_403

TeslaIsBae

Wed Sept 02 2015, 05:15PM

Registered Member #55171 Joined: Fri Jun 05 2015, 06:44AM
Location:
Posts: 9

Hello!

I am a student and I am writing an essay on Tesla coils and how they light up bulbs, such as neon tubes. I have built a small model Tesla coil. I will provide more information about it at the end, in case it is necessary. But basically, I can get a neon bulb to light up but I can't figure out how this process happens. There really isn't much information about this online. I know exactly how a neon bulb works so I'm guessing that the Tesla coil must have an electric field.

Therefore, my question is: what makes a neon bulb light up when it's in the close proximity of a Tesla coil. The more detailed the process is, the better.

As to the model coil that I am using; I've built a small DC coil using a bug zapper that is powered by two 1.5V batteries. I am aware that this isn't really a Tesla coil but just an air-core transformer but it is fine as model for my essay. And it causes a neon bulb to light up, so I am assuming that the process is the same as with a real Tesla coil.

Thank you in advance! :)

Richard

hen918

Wed Sept 02 2015, 05:40PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

The air and the glass of the non acts a capacitor, the "Tesla coil" a high frequency high voltage source (with a huge electric field) and the neon is the load.
The tesla coil is sending out a hell of a lot of electrons. Some of these are energising your neon.
The more complex answer involves capacitive coupling (the air is the dielectric of the capacitor)

TeslaIsBae

Wed Sept 02 2015, 06:03PM

Registered Member #55171 Joined: Fri Jun 05 2015, 06:44AM
Location:
Posts: 9

Thanks, that makes sense how the air and the glass of the bulb act as capacitors that then discharge into the neon gas, the load. So if I understand it correctly, by the "energising neon"you mean the Tesla coil's electric field pushes electrons into the neon bulb? Those then ionise the neon gas, which releases free electrons, excites them and the process is then that of a normal neon bulb.

hen918

Wed Sept 02 2015, 07:05PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

TeslaIsBae wrote ...

Thanks, that makes sense how the air and the glass of the bulb act as capacitors that then discharge into the neon gas, the load. So if I understand it correctly, by the "energising neon"you mean the Tesla coil's electric field pushes electrons into the neon bulb? Those then ionise the neon gas, which releases free electrons, excites them and the process is then that of a normal neon bulb.

Umm, yes, basically... The only difference between using the neon normally and with a tesla is that usually you use wire to conduct the voltage, not air! Neons only need very small currents to light which is what lets them light through the ionised air around them.

TeslaIsBae

Wed Sept 02 2015, 07:20PM

Registered Member #55171 Joined: Fri Jun 05 2015, 06:44AM
Location:
Posts: 9

Perfect, thank you very much. Sorry for sounding so primitive sometimes; I still have a lot to learn :)

Antonio

Wed Sept 02 2015, 09:26PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

The Tesla coil does not have to push electrons against the tube (what it would do only if actually sparking to the tube). It produces an intense electric field around it, and the low-pressure gas inside the tube gets ionized just due to this, without need of an external power source connected through wires.

TeslaIsBae

Thu Sept 03 2015, 02:14AM

Registered Member #55171 Joined: Fri Jun 05 2015, 06:44AM
Location:
Posts: 9

I've noticed that the bulb shines extremely bright when there is a spark constantly jumping to it, but it gets dimmer when it is just being excited by the electric field. Is the process that light the bulb up the same when there is a spark jumping to it and when there isn't? Is it simply that a lot more electrons are discharged into the neon bulb when a spark jumps to it?

dexter

Thu Sept 03 2015, 06:31AM

Registered Member #42796 Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195

i don't like this "the intense electric field ionize the neon" i want more i want to know how
Could it be due to the low pressure neon having a lower resistance than air thus developing a potential difference between different regions of the glass placed at different lengths from the source of the electric field (inverse square drop with distance of the value of the field in different points)?

this explains why a neon lights up even when isolated from ground or other objects?

Dr. Slack

Thu Sept 03 2015, 07:50AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

There are two completely separable issues here. How a neon bulb lights when connected by wires to a power source, which is an interesting enough problem in its own right, and how a TC gets power to it through the air.

Which does the OP want to know about? If both, let's deal with them one at a time, using the most appropriate description for each. The neon will need electric fields, electrons, ions. Power through the air is better handled with just electric fields, capacitance, displacement current. If an arc jumps TC to neon, then we're back to electrons and ions again.

Uspring

Thu Sept 03 2015, 10:04AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

The low pressure in the neon tube will make the gas inside it conductive at much lower electric field strength than necessary e.g. in the air surrounding it. It can therefore light up at distances far outside the reach of arcs of the coil. So why doesn't the tube light up near a high voltage DC source like a van de Graaff generator?

Say you have a VDG charged up to a high positive voltage. Then the electrons inside the tube will be pulled towards the VDG and the positive ions repelled from it. That will cause a field inside the tube against the direction of the VDG field. So there will be no field in the tube and no light.

A Tesla coil produces a high frequency AC field. That causes a permanent flow of electrons and ions back and forth between the sides of the tube facing the coil and opposite from it. The tube will light up.

If an arc hits the tube, there is a conductive path from the TC to the tube, which causes the high electric field of the TC top to be transported into the vicinity of the tube. The tube will be much brighter then.

1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob