Tag Archives: electricity

Not The Alom Shaha Motor

One of the great joys in my life is to come across a new science demo, particularly if it’s an elegant, simple one. I can take credit for introducing one of my favourite science communicators, Michael de Podesta, to this demo of the motor effect. Michael kindly calls it the “Alom Shaha Motor” but I can only wish that I came up with this idea myself. Jonathan and I have made a film about this, but here’s Michael’s own, elegant, simple film of the demo.

Electromagnetic induction

Thanks to one of the IOP’s twitter streams for reminding Alom and I of this film, which we’d rather forgotten about. Unlike many of our other demo videos, it wasn’t made for the IOP/National STEM Centre, nor for Get Set Demonstrate. Rather, we threw it together to enter a slightly weird competition. We held out little hope of winning, but the prize fund was considerably larger than any demo filming budget we’ve ever secured, so we had the (odd?) thought of using the winnings to fund the project we actually wanted to do.

Happily, our friends Andrew and Sharmila Hanson won, and did fabulous things with the cash, so we’re hardly complaining. (Oh, and: belated happy birthday, Andrew!).

Our EM induction film, meanwhile, ended up being loaned to the National STEM Centre so it could sit alongside the films we did make for them. The YouTube version above is still higher-quality, if you want to download it.

Funny how things turn out, sometimes. Also: I’ve just received a text from Alom complaining about how rough he looked three years ago. Tee-hee.

Electric Semolina

I hope that most school children get to see that sprinkling iron filings around a bar magnet produces a pattern which shows the shape of the magnetic field around the magnet. It’s a very simple, yet useful, way of making something invisible, visible. What many school children won’t get to see is that you can do something very similar with electric fields, using semolina instead of iron filings. The picture above is from a demonstration I showed my year 13 (A-level) students last week – the instructions for how to set it up can be found at the Practical Physics site.

A tip: it’s lovely for the students to see this for themselves, but the apparatus is tiny so use a camera to project it onto your whiteboard as well. I forgot to take my webcam into school so I used my phone to take a photo and put that up on the whiteboard so we could look at the demonstration closely and discuss it. I encouraged my students to take photos too, as I did when we investigated magnetic fields – I’m not convinced getting students to draw what they see is terribly useful in this case. What do you think?

Banana voltaic pile

via Twitter this morning, chemistry lecturer Mark Lorch:


Potatoes? Yes. Lemons? Absolutely. Not sure I’ve seen a banana pile before, though. Mind you, if you’re going to build a little tower of the things you might as well use acid-soaked paper anyway…

Nice twist on a familiar concept.