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This was my grandfather’s and have no idea what it is only that it is some piece of physics equipment!

The main black cylinder doesn’t seem like it wants to rotate but not sure if it should?

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    $\begingroup$ I'm voting to close this question as off-topic. $\endgroup$ – AccidentalFourierTransform Dec 11 '18 at 16:14
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    $\begingroup$ @AccidentalFourierTransform: How about explaining why you think it's off-topic? It seems obviously on topic to me. $\endgroup$ – user4552 Dec 11 '18 at 16:31
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    $\begingroup$ @AccidentalFourierTransform While it is not clear cut ( maybe a topic for meta) I would happily class this as a "experimental design" question as it is clearly physics equipment meant for some experiment. This would put it squarely on topic for the site as per the help section. Equally other similar questions have been posted before and been accepted e.g. physics.stackexchange.com/questions/298079/… $\endgroup$ – J.Doe Dec 11 '18 at 16:49

It looks like an induction coil with the make and break device at the bottom and a switch right at the bottom. If you connect it up to an accumulator, be very, very careful as the output between the two balls, when separate, could be lethal. Also the electrical insulation elsewhere may be poor and you might get a shock just by touching the switch.

Use with very great care and preferably have somebody who knows about such devices with you.

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  • $\begingroup$ Yup, I played with one of these as a child. $\endgroup$ – mongo Dec 11 '18 at 16:09
  • $\begingroup$ Thanks Farcher - I will be careful! By an accumulator do you mean something like a Van de Graaff? How would it be hooked up? Would the small balls across the top need to be moved apart? What is the actual point in the apparatus/what would it be used for? $\endgroup$ – user37250 Dec 11 '18 at 18:15
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    $\begingroup$ An accumulator is a lead-acid battery of the type used in cars but those are 12 V. That can delivers a reasonably large current but I would start with a 2V battery or power supply. If not enough you can always increase the voltage having not burnt out the primary coil. You will then have to adjust the make and break device (interrupter) but do not do this whilst the coil is live unless you do this with a polythene (insulator) rod. $\endgroup$ – Farcher Dec 11 '18 at 18:40
  • $\begingroup$ Thanks. Ok so I think I have got it. Do the leads for the battery I use connect to the notches either side of the lever switch thing? Should the lever be up or down before connecting the battery? Once the battery is connected should there be a spark between the balls? What does that springy tapper do to the right of the lever? Do I do anything with that? $\endgroup$ – user37250 Dec 11 '18 at 21:56
  • $\begingroup$ You are correct about it being an induction coil. Looks like this one: $\endgroup$ – user37250 Dec 11 '18 at 21:57

It is a spark radio transmitter.

The first working radios.

Video: https://www.youtube.com/watch?v=YSf93g0heUA Pics: https://www.google.com/search?q=spark+radio+transmitter&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi-68m5vJjfAhXMx1kKHVuUASQQ_AUIDygC&biw=1920&bih=930

This one looks awfully similar and might give you some help finding out model and such:


Remember 300 baud modems that you put the handset into? This was the top of the line once upon a time too. It's why we have "SOS" in our language rather than relying upon a simple "Oh God, we need help!"

And if Tesla'd ever realized be was using Morgan's money to succcessfully invent radio transmission rather than failing at wireless power transmission, we'd've never called these "Marconi Spark Gap Transmitters"... but he didn't.

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    $\begingroup$ Although induction coils were used as radio transmitters many years ago it is probably illegal to use one for this purpose nowadays as it would produce electromagnetic waves over a very large range of frequencies (bandwidth) thus producing radio frequency interference (RFI). $\endgroup$ – Farcher Dec 11 '18 at 22:15
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    $\begingroup$ @Farcher It's definitely illegal, at least anywhere with laws that govern RFI and the EM spectrum allocations (ie: ITU members, etc, which is most everywhere with laws at all). $\endgroup$ – J... Dec 12 '18 at 12:58
  • $\begingroup$ Though generally banned, you can get special licenses to operate spark gap transmitters. They did that, for example, as a 100th anniversary re-creation of Marconi's transatlantic message. (As I recall, the re-creation of the original coherer didn't pick it up and they only got the signal on a modern transistor receiver) $\endgroup$ – user71659 Dec 12 '18 at 17:47
  • $\begingroup$ @user71659 I would imagine that there were plenty of engineering controls and studies done for that test. I'm also quite sure that the timing and duration of the test must have been very carefully planned and controlled. The last thing you'd want is, for example, to leave a million tons of aircraft circling airports with Victor out to lunch. $\endgroup$ – J... Dec 12 '18 at 23:21
  • $\begingroup$ @J... I doubt they thought about it too much, broadband noise occurs naturally and accidentally everywhere. Lightning, arcing power lines, welding, malfunctioning auto ignitions, etc. I suspect they just showed they were transmitting with nobody around and for a brief time, not by an airport. $\endgroup$ – user71659 Dec 12 '18 at 23:46

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