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    • #12591
      Profile photo of Andrew Normand

    • #12592
      Profile photo of Andrew Normand

      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

    • #12593
      Profile photo of Andrew Normand

      What happens if you use a smaller ball?

    • #12594
      Profile photo of Andrew Normand

      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?

    • #12595
      Profile photo of Andrew Normand

      Here is mine running with a smaller pith ball.

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

    • #12596
      Profile photo of Andrew Normand

      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

    • #12597
      Profile photo of Andrew Normand

      Nice sparks!

    • #12598
      Profile photo of Andrew Normand

      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?

    • #12599
      Profile photo of Andrew Normand

      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.

    • #12600
      Profile photo of Andrew Normand

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

    • #12601
      Profile photo of Andrew Normand

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

    • #12602
      Profile photo of Andrew Normand

      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. 

    • #12603
      Profile photo of Andrew Normand

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

       

    • #12604
      Profile photo of Andrew Normand

      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

    • #12605
      Profile photo of Andrew Normand

      Great job Drew – much neater than mine!

    • #12606
      Profile photo of Andrew Normand

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

    • #12607
      Profile photo of Andrew Normand

      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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