"Peter Hucker" wrote in message
newsp.tmzeq8ks4buhsv@fx62...
On Sun, 28 Jan 2007 23:03:36 -0000, colin
wrote:

"Peter Hucker" wrote in message
newsp.tmvmiiqt4buhsv@fx62...
On Sat, 27 Jan 2007 01:38:36 -0000, colin
wrote:

"Peter Hucker" wrote in message
newsp.tmrzqxxk4buhsv@fx62...
On Wed, 24 Jan 2007 14:53:25 -0000, Snap Whipcrack..............
wrote:

It dissipates. Where do you think the microwave transmitters on
mountain
tops power ends up? It doesn't go round and round the earth
forever.

It's absorbed into water, in lakes for example.

A closed microwave has nothing that can absorb it.

The glass tray will usually absorb some of the microwave, basically
when
its
empty the electric field builds up to such a high value that it
eventually
gets absorbed by something somewhere, or it ends up disipating in
sparking
wich can be quite spectacular if have two bits of unconnected metal
close to
eachother.

Brainiac Science Abuse (TV program) put a set of five swinging balls
(one
of them office toys) in a microwave on its own. The microwave exploded
spectacularly after less than a minute. Can you explain that?

From what ive seen of braniac they probably filled it with something
that
would explode spectacularly.
I wonder what the balls were made of, something explosive perhaps ?
ordinary flour or paper dust can make a very good explosive if mixed
with
air.

You mean they were lying?!?

well normally in order to cuase an explosion you have to have a combustable
material that burns very quickly,
the force comes from the fact that the burnt material wich is oxidesed takes
up a great deal more volume
and until it expands is under great pressure. in an empty oven there is no
combustables.

they always seem to try something to see if it blows up and if it doesnt
then they make sure it does, its often a caravan or microwave oven that gets
blown up.

A colleague suggested that large metal objects might "short circuit" the
magnetron and draw more power from it than it expects. I didn't agree or
disagree, I know nothing about that sort of thing.

It cant 'draw' more power from it unless that power actualy goes somewhere,
however it can put the magnetron under more stress, the voltages and current
may be higher even though the power is actually less, ie they are out of
phase and hence arnt both high at the same time.

but theres actually not that much to a magnetron, theres a central cathode
wich is like a rod with a heater inside, and a circular anode around this
with slots in, all in a vacuum and also not surprisngly a strong magnet.
The power is picked up via a piece of wire inbetween one of the slots.
The anode is what gets hot due to current flowing and is attatched to a
quite large heatsink with great number of fins wich has a fan blowing on it.

theres not a great deal to go wrong, its simplicity is its strength, the
same basic design was used 60 years ago, it could lose the vacuum of course,
or the insulation could fail, or the heater could break, or the magnet could
lose its strength but most of the parts are designed to work at a high
temperature, its just metal and glass, its not like silicon wich self
destructs at 200'c.

The transformer does actually limit the current anyway.

Colin =^.^=