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#130448 - 05/18/06 05:21 PM air
marsbar Offline
Member

Registered: 04/04/06
Posts: 31
Loc: london, ont, canada
What is the resistance of air, not too complex and use 1ATM. Thanks

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#130449 - 05/18/06 05:51 PM Re: air
LarryC Offline
Member

Registered: 07/05/04
Posts: 776
Loc: Winchester, NH, US
Dry? I believe it is about 10 kV / inch

LarryC

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#130450 - 05/19/06 02:13 PM Re: air
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Relative Dielectric Strengths of Gases: (0.1 in ga')

Air: 0.95,
N2: 1.0,
CO2: 0.90,
H2: 0.57,
A: 0.28,
Ne: 0.13,
He: 0.14,
SF6: 2.3 - 2.5,
C1F4: 1.1,
C2F6: 1.9,
C3F8: 2.3,
C4F8: 2.8,
CF2CL2: 2.4,
C2F5CL: 2.6,
C2F4CL2: 3.3

Sphere-gap Spark-over Crest Voltages:
(from AIEE Standard No. 4)
At 25┬░ C and 760 mm Barometric Pressure; one sphere grounded.
_____________________________________________

Sphere Diameter = 6.25 cm:
--------------------------------------------
---------------------------------------------
Sphere Gap Spacing, in cm: 0.5 cm
60 Hz, Negative Impulse KV Crest: 17.0 KV
Positive Impulse KV Crest: 17.0 KV,

Sphere Gap Spacing, in cm: 1.0 cm
60 Hz, Negative Impulse KV Crest: 31.3 KV
Positive Impulse KV Crest: 31.3 KV,

Sphere Gap Spacing, in cm: 1.5 cm
60 Hz, Negative Impulse KV Crest: 44.5 KV
Positive Impulse KV Crest: 44.8 KV,

Sphere Gap Spacing, in cm: 2.0 cm
60 Hz, Negative Impulse KV Crest: 57.0 KV
Positive Impulse KV Crest: 57.4 KV,

Sphere Gap Spacing, in cm: 2.5 cm
60 Hz, Negative Impulse KV Crest: 68.8 KV
Positive Impulse KV Crest: 69.3 KV.

I am sure this is not what you are looking for, but it may be of some assistance.

Scott35

btw, I seem to remember a figure of 100 KV / Meter in moist air ( >85% Humidity, < 29.00 mbar ), for the dielectric breakdown point of a "Typical" mole of air. This was in reference to Lightning.

LarryC's reference to 10 KV / Inch for Dry, "Clean" Air sounds familiar also.

Scott 35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#130451 - 05/19/06 03:05 PM Re: air
marsbar Offline
Member

Registered: 04/04/06
Posts: 31
Loc: london, ont, canada
Thanks guys, if I am correct it the amount of voltage required to arc through a given amount of air as in sphere to sphere.

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#130452 - 05/19/06 06:10 PM Re: air
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
marsbar

Correct.

The listed Voltages are the Minimum Voltage (or Potential) between the two spheres, where the Dielectric Strength of the Air will breakdown and allow an Arc to form between the two "Electrodes".

The Arc leads way for a Plasma to be created, if there is sufficient Amperage available to create one.

The size of the Plasma, its intensity, and such, depends on the available Amperes which may be transferred across the gap - and in the long run, the total amount of Electrical Power available (in both True and Apparent forms - more accurately, total Reactive Power for an A.C. system, or simply True Power for D.C. systems).

Once the Plasma is formed and "Somewhat Steady" Current is flowing, the Potential Difference (or voltage) between the two spheres becomes reduced, as the Plasma is highly conductive (ref. "Negative Resistance").

This is getting kind of complex, so I will stop here

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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