OT: it's not the volts that ...

[Andy Burns]

[Chris J Dixon]

One of the most impressive bangs I saw was at Switchgear Testing Company in Trafford Park. Most of the adjacent Alstom site, where I had once worked, had gone, and this remnant was a sad shadow of its former self, with weeds growing through the concrete. Looking at the mapping sites, it now looks as if all traces have been removed.

The device under test was a railway shoe fuse, intended for the dc Electrostars. It consists of a bare copper strip in an open-sided fibreglass enclosure, which contains hidden metalwork to produce a magnetic blowout effect.

We did a trial shot at 10 kA for 1 second, which merely caused a slight colour change. At 30 kA, I was very glad to be behind the ballistic glass. As the copper strip blew apart the shower of sparks was terrific.

We needed to do the test because for Electrostar we had to change the incoming cable orientation, to suit the underframe layout, and there was concern that this might have an effect upon the blowout action. As it happened, all was well.

Chris

[Brian Gaff]

Have you ever seen that documentary about Mr Megavolt, who keeps a huge Tesla coil in his truck and performs on the roof in a chain mailsuit and conductive gloves. There are many cautionary tales in that about how the general public have no clue and so he needs security guards to stop them climbing on, and how his very thick boots once caught fire while he was wearing them etc.

Brian

[Andy Burns]

I've seen a few tesla coil vids.

In case you didn't watch, this one is using 100 car batteries in parallel to melt things ... though he ends up using series/parallel to get about 60V instead of 12V

[Tim+]

Must admit I got bored pretty quickly. I was hoping for ball lightning or something more exciting than melting stuff.

Tim

[Brian Gaff]

Well obviously when I say see, I mean hear, but I'm sure we all experimented with high voltage generators back then. I doubt if it would be considered safe to charge up people standing on a rubber mat these days though, would it?

I built a very simple tesla coil on the stem of an old car tappet. Just a doorbell in series with a battery and the coil was enough make it glow purple on the top of the winding. Brian

[Brian Gaff]

The Mr Megavolt one was recently on Samsung TV plus, which was a freeby. By all accounts it was pretty spectacular with huge sparks and blobs flying about. It did highlight though, the huge lack of knowledge of electricity in general by the public. As the thread says, its not the voltage, but the current that will kill you, but even so, from my own small scale experiments you can burn yourself with continuous sparking. Brian

[Tim Streater]

Havng the opportunity (while I was at CERN) to go inside a room-sized 1-Tesla electro-magnet was quite interesting. Remove all metal from self before entering. Given a baked-bean-tin-sized solid lump of aluminium to hold, the interesting thing was the ways inwhich you could move it easily, and the ways in which it absolutely resisted movement. You could move it sideways, f'rinstance, but you couldn't tilt it. Stand it on its edge at an angle and it would only topple over very slowly.

[Peter Able]

ITIYM "It's the volts that jolts, but the mils that kills"

[Peter Able]

You need some ammonium bifluoride.

Put a bit in a sink, then wet it. Sceptics say "is that all?" They then gasp as the sink disintegrates. Metal or Ceramic, though metal is far quicker! This stuff even dissolves quartz.

PA

[Alan J. Wylie]

More of this sort of thing in Derek Lowe’s "In The Pipeline" blog.

[Vir Campestris]

"all metal from self"??

Does that include dental fillings?

Andy

[Tim Streater]

Apparently not :-)

[The Natural Philosopher]

Nor stents...

[NY]

How does MRI cope with non-removable metal like fillings and stents?

Do they just work around it and concentrate the magnetic field into a "beam" that avoids the stent etc?

[The Natural Philosopher]

I think the stents simply show up, but they are small enough not to distort the overall picture

[SH]

With cochlear implants, you had to remove the magnet first, leaving just the electrode array in the cochlea.

In this case, you are limited to a MRI scan using no more than about 0.5 Tesla IIRC.

if you needed to go above 0.5 T for medical reasons then the electrode array would have to be explanted, then the MRI done and then the array re-implanted, and this is not a trivial thing to do surgically.

[NY]

Surely the problem isn't that the MRI picture may show local flaws, but the much more serious problem that metal objects will get currents induced in them that will causing burning - or if the objects are magnetic, they will be attracted so strongly to the MRI magnet that they will be ripped out of the body.

[Peter Able]

Right!

Actually, my problem is how to dispose of the 2.9kg I have left over from a 1974 purchase of this substance. I've no confidence in our local disposal services, and suspect that they'd just pour it down the drain.

Our should I say "Soon to be ex-drain"?

[Tim Streater]

Giggle opines that you mix with lime or calcium hydroxide. And plenty of water.