Use Discussion….

When I first came across these my friend rang me up and described it over the phone to me as I built it. They are very impressive, thanks again for sharing Dan

What happens if you use a smaller ball?

Great session, nice demo. I have a couple of questions I hoped you could answer…

The ball you used in your demo was pretty large and moved quite slowly, have you tried smaller ones and do they move any more quickly?

Does using the higher p.d. from a Van de Graaf make a significant difference, or is a lab EHT supply just as good?

Here is mine running with a smaller pith ball.

Smaller mass but I suspect less surface to pick up charge?

Yes thanks Dave – I have had similar results with a smaller ball. With a larger ball however it is possible to short out between two of the contacts on the bowl resulting in sparks

Nice sparks!

Up here in Scotland there are some very risk-averse people who might be worried about using an EHT supply with croc-clips connecting to the foil strips.

Could the strips be hard wired in some way to leads with shrouded plugs?

If you got a long shrouded lead and cut it in half, bared the end, and spread the strands, you could stick that under the foil couldn’t you? The other end of the half cable would still be shrouded.

As Dan says another way to run this is with a Van de Graaff

Thank you for the particle accelerator.  Can’t wait it try it out. 

I see you get arcing at the base. I had the same problem though not as much. I’ve been thinking that I should stop the uncrossed ones further from the bottom to increase the spacing. I get a similar speed but have seen the balls flying around like a wall of death on youtube clips, I’m hoping that increasing the spacing at the bottom may increase the charge available so the ball can pick up speed. 

Very pleased with the results. Thanks agin for running the session, Dan.

 

That’s working brilliantly Drew, much better than mine. I think I need to do some fine tuning, mine works the same as David’s. I was hoping for the ball to climb the sides of the bowl like yours

Great job Drew – much neater than mine!

Really good, thanks. How do you use this in lessons?

One way I use it is as an interesting starter when doing cyclotron with A2 students. Can they explain how the ball is made to move in a circle? This then leads on nicely to dee’s with electric fields for acceleration of charged particles.

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