I feel it is cold filament effect and lack of zero crossing switching of Power supply
-- to clarify, if the switch on takes at a time the voltage is transiting or is at peak, this cold filament would draw heavy load.
the circuit breaker(if not thermal) would sense it and trip

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Regards,
Sarma.

 

What you think and the actuality in the real world are evidently not the same. A wrench across a car battery will actualy exlpode if the conncetion is good. Do you have any idea of a car battery current output during a short across it probably not. a "D" cell can deliver 2 amps try it.

 

The short circuit current will depend on the condition and charge of the battery.

My reasoning was that the battery terminals are normally made of lead which has a higher electrical resistance and lower melting point than a wrench so it's more likely to melt.

In reality I don't know what would happen because I'm not stupid enough to try it; I take it you've done it before or you wouldn't be so confident in describing it.

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http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

One reference says the welding arc voltage is 17 to 45V. And I believe the voltage across a carbon arc lamp is about 35V.

__________________
Carl

 

Yep--my welder says 27 volts. I typically weld smaller mild steel so I tend to set it to between 25-80 amperes.


Torben

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Curiosity was framed. Ignorance killed the cat.

 

Locked rotor current though the starter motor for my '94 Honda Civic is 400 A [@ 4 v across the motor] so the internal resistance of this battery = (12-4)/400 = 20 mΩ, so Isc = 12/.02 = 600 A.

This should melt #6 copper wire.
What is the fusing current for a wrench?

 

For example: a group 27 standard GM pick-up batteries short circuit current is around 4000 Amps for 1 second. Car batteries vary in design and are very model dependant.

Re: #6 AWG or GA. wire melting at 600 Amps...it depends on the time the current flows; it will not vaporize and the motorcycle battery would not be able to sustain a voltage long enough to melt the #6 wire...the insolation on the other hand would melt if it was not made of hapalon.

 

Which gives 100x the heating effect in a conductor.
Wear face protection, drop the wrench, post the video!

 

The resistance of a 6 GA. copper conductor is between .00395 and .000465 Ohms per foot, 12.58 feet per lb (depending on strand count and copper quality.)and the meting point is 1083.0 °C (1981.4 °F) at sea level. The energy required to melt copper is 688 J/g.(g.=0.0022 pound)

If you know the appoximate length...Bob's you uncle.

 

Battery designs are very differant, a 75 pound battery LA (Lead acid battery) can have 1/16, 1/8 or 1/4 inch thick plates and the surface area of the plates can vary greatly base on the design of the battery. the nominal voltage is usually of each plate is 2 VDC but the short circuit current is really determined by the sum of the surface area of the total number of plates. The short current circuit is supplied by the discharge of the surface of the plates, long rate discharge is dictated by the thickness of the plates of the total mass.

 

Regarding th wrence on the battery terminal thing...let's say, if the melting point of the wrench (probably chromoly) is 3 times the melting point of lead, and the contact area of each battery terminal to wrench is 4 times that of the circular dimention of the wrench handle, the wrench will melt if the battery has the availability to deliver enough current to raise the chromoly above it's melting temperature.