Lieutenant Scott wrote
Rod Speed wrote
Lieutenant Scott wrote
Rod Speed wrote
Lieutenant Scott wrote
Rod Speed wrote
Lieutenant Scott wrote

Not clear what you mean there.

As I understand it, there is a hole at the side of the oven cavity. Behind that hole is a magnetron that produces
microwaves,

Yes.

and next to it something to absorb any microwaves which happen to
bounce back in there, so they don't damage the magnetron. There's some kind of T shaped thing between them to
direct the
microwaves the right way.

I dont believe there is now.

Now if the ballast can't absorb all the power the magnetron can produce (which would happen if there is no water
in the oven to absorb any), then something will catch fire.

So it makes much more sense to measure what gets reflected
and cut back what the magnetron is producing instead.

And thats the way its done.

And it doesnt cost much to do that.

I thought there was always some reflection

Yes, thats why you MEASURE what gets reflected.

(the waves that happened to hit the hole before the food), and
magnetrons hated even the smallest amount coming back.

No, that last isnt right.

I suppose a test could be done..... measure the power the microwave
oven consumes from the mains with different things in it.

In fact..... [pulls energy meter out of cupboard]

And the results for a £20 Tesco cheapy microwave a

Nothing: 1135 watts
A mug with a tiny bit of water in it: 1165 watts
A mug full of water: 1185 watts

Very odd. There is only a SLIGHT reduction in power consumption the less stuff there is in the oven.

So it appears it's not reducing the magnetron power,

It clearly is when its empty.

and when it's empty, all the power is going somewhere, presumably as heat in the workings of it, which can't be good

It clearly works fine.

- perhaps eventually it would overheat and cut out. Or break.

The modern branded ones dont break.

Since all the modern branded ones have mulitiple power levels
selectable, presumably they just reduce the power level as required.