In message <[email protected]>, dated Fri, 29 Mar 2013, Richard
Nute <[email protected]> writes:
If the circuit is open, then, I suppose, I could apply a high
enough voltage to cause a breakdown at the point where the
circuit is open. The voltage would need to be more than 323
volts as air does not break down below that voltage (Paschen's
Law).
The putative bad contact is not an air-gap but an oxide layer. Ps you
know, the breakdown voltage of such layers is quite low (as in
copper-oxide rectifiers), but is several volts.
If I remember correctly, the applied voltage was limited to 6 V in a
former edition of BS 415, long before it was fully aligned with IEC 65.
We actually see this effect in some types of switch; there is a range of
European mains switches that is well-known for not working reliably at
12 V or less. It was also an issue in push-button switches used for
function selection in radios, etc. of the 1960s-1980s.
--
OOO - Own Opinions Only. See www.jmwa.demon.co.uk
Which Thunderbird will David Miliband pilot? Or will he drive Lady Penelope?
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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