"NY" wrote in message
o.uk...
"michael adams" wrote in message
o.uk...
You're not seeking to do that deliberately, but it may happen -
especially if the bulb is hard to get out due to having been screwed in
too tight.

Screw in light bulbs were developed by Thomas Edison.

It would be interesting to know the precise details of the thousands of
experiments
he must have conducted at Menlow Park which led him to conclude that
screw fittings
are in any way superior to bayonets.

Yes, I'd love to know what made him go for a screw thread. It has so many
disadvantages:

a) outer screw is connected to one or other of the wires, so there is a
50:50 chance that it will be live when you are changing a bulb

b) it takes longer to unscrew a bulb, involving several 360-degree turns,
than to remove a bayonet that requires maybe a 10 degree turn

But you do that so rarely that its no big deal
and its much more secure in an ES socket.

c) because there is a lot of surface area contact between bulb screw and
fitting screw, there is much greater friction and much greater chance that
corrosion or a slightly oval fitting/bulb will cause the bulb to bind in
the socket

Never had that happen, even with external bulbs.

The third is the biggest problem.

Nope.

I've found that a bulb which has been in its socket for several years has
stuck to the fitting,

Never had that happen with ES bulbs and almost all of mine are.

even with bayonet, and the glass has become loose from the metal. The
usual mode of failure in those cases is that you press and twist, and the
glass comes away, leaving the metal cap in the holder. If that is possible
even with a bayonet, think how much more likely is is to happen with a
screw fitting.

Never had that happen with ES bulbs and almost all of mine are.

And yet not only the US but also a lot of mainland Europe uses these
stupid fittings.

Nothing stupid about them.

I'd always thought that it was a 120V versus 240V thing (to prevent a 120V
bulb being used accidentally on 240V), until I saw that all the light
bulbs that are sold in Ikea have screw fittings, so evidently those are
used in Sweden.
In fact they are much more common world wide than bayonet.