Dual CPU nodes?

Robert G. Brown rgb at phy.duke.edu
Tue Oct 22 09:48:14 PDT 2002

On Tue, 22 Oct 2002, Ken Chase wrote:

> Me too, this is why I am asking - what other kinds of semi-standard wiring
> and transformer configurations found in a typical lab (thats not a power
> electronics research lab, nor has megawatt lasers in it :) that could
> cause this? can you think of any configuration that would result in this?

Short of a nearby cyclotron magnet (something with a field in the Tesla
range) no.  The basic problem is that 10^7 T-m/A constant -- it is
really hard to get ANY reasonably measurable force for currents in the
ampere range and distances in the cm and up range.  That's why chunks of
metal aren't bounced around by inductive surges every time you flick the
lights on and off (which does, after all, drop currents order an ampere
within cm or less of e.g. nails and screws in ordinary construction).

Just the energy involved is puzzling.  To lift an arm (mass perhaps a
few kg) order of 1 m requires order of a few TENS of joules, forces (to
overcome gravity and impart that energy in less than one second) on the
order of hundreds of Newtons.

I use magnets scavenged from dead hard drives on my refrigerator.  They
are so strong that I have to pry them from the surface to remove them
and can easily hold up a newspaper.  Still, the force they exert on the
refrigerator is negligible ten cm away, and I doubt that the energy
binding it to the refrigerator is more than a few joules because of the
extremely rapid dropoff of the magnetic field.

Maybe the earlier suggestion of a transformer (or some other really huge
electromagnet) nearby powering down at the same time, together with a
monster bus carrying a lot of current.  Maybe a passing monopole.  Maybe
some local oddity in the wiring has led to the inadvertent discovery of
the fifth force.

Of these, the transformer sounds best.  When cranked up, the magnetic
field in a transformer or some other big magnet can hold a lot of
energy.  If the field collapses in the right way, it can make a
significant inductive electromagnetic pulse (remember "Small Soldiers"
where they fried the toy's circuits by shorting out a big transformer)?
It just seems pretty unlikely.  I've worked with electricity a long time
and cannot recall seeing a physical coupling like that.  I'll ask my
brother-in-law the electrician -- if this sort of thing is common, they
must warn professional electricians about it since they work within a
few feet of high voltage busses that would kill them dead if their arm
were jerked against it every time a nearby circuit were switched on and
off and they happened to be wearing a watch or bracelet.

16000 volts can ruin your whole day.


Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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