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Suggestions and thoughts on my magnets and magnetism demonstration

  1. Mar 27, 2014 #1
    I hope that the title is a bit better than my last one...

    I would appreciate any input on items I have made or will be demonstrating as it should be about 30 minutes long and a balanced programme.

    Background... I am in training as an Assistant Beaver Leader in my Sons Beaver cubs scout pack and one of the badges that they are doing asks for a demonstration of something mechanical or something that uses magnets.

    Keep in mind that beaver scouts are 5yr 9months to the age of 8 years, so we have very inquisitive minds here and likely very difficult questions to answer.

    What I have devised are a number of demonstrations that I hope to get the Beavers engaged in, however, I have a some safety concerns, see end of lists. So a bit of guidance on this would be appreciated as well as any comments that add to or enhance on the demonstration will be welcomed as I have a 30 minute slot, 20 minutes demo and 10 minutes discovery.

    I have listed the demonstrations as follows (in no particular order.)

    1. Ask if anyone knows what magnetism is.
    2. Discuss magnets, magnetism and uses.
    3. Demonstrate Magnets and Magnetism.
    4. Discovery and investigation.

    The Demonstration
    • Electromagnets, I used standard 13amp (Power) and 3amp (Lighting) cable to make a couple of electromagnets, the 13 Amp is a 5cm long single layer 20 turn magnet, the 3Amp cable is a 3 layer 15 turns per layer and this is to demonstrate the strength of the electro magnet based on number of turns and the input voltage is just under 5 volts via 4 rechargable 2000mAh batteries.

    • Solenoid, I used 3Amp cable in the same configuration as the electro magnet wound around a cylinder former. Input voltage is under 5 Volts with 2000 mAh rechargables. This is to demonstrate linear motion / pull through an electromagnet.
    • Use a piece of formed copper wire and couple of N42's and a 1.5 volt Alkaline battery to make a crude motor to demonstrate circular motion
    • Demonstrate that a compass aligns to a magnetic field or is influenced by an external magnet or a charge through a wire.
    • Lenz's Law, the pretty cool and I can't help myself with this one, dropping a neodymium magnet down a copper pipe, and it doesn't get old demo... this one I plan on dropping a metal screw, an aluminium piece of metal through before showing that the copper pipe is not magnetic and then dropping the magnet down it after a little bet on how long it will take to drop, so far the best time is 8 seconds with 3x N42's (10mm dia x 3mm)
    • Show that a copper tube is like a wire and a current can be induced via a magnet, my electric meter is not sensitive enough but I can sometimes register 0.03 mV with the N42's
    • Iron filings used to show the invisible lines of (is it force or energy?) between the poles of a magnet. (Alnico magnet not N42's)
    Then after the demo ( I intend on doing the messy stuff!)
    • Use a compass to plot the lines of force on a piece of paper
    • Show a video of how magnets are made
    • Let the Beavers try the Lenz's Law demo themselves.
    • Metal sorting, use a magnet (Alnico educational magnet) to sort a variety of metals that are magnetic and non magnetic.

    Now my concerns...

    The wires get hot, as to the batteries, can I do anything to limit or stop this?
    The power source for most of the demos is a 4 x 1.2 ~ 1.4v 2000 mAh cell in series so the output is almost 5 Volts and other batteries wil be single cells of 1.2 ~ 1.5 volt.

    would I be correct that the wires are getting hot and cells getting hot because the total amperage is 8 Amps in the 4 Cell experiments? What are the risks? Could one of the cells explode or wires catching fire, etc?

    Any suggestion are welcome.
    Last edited: Mar 27, 2014
  2. jcsd
  3. Mar 27, 2014 #2
    Firstly i'd just like to say that this sounds brilliant!

    I loved Beavers, Cubs and Scouts because of the effort the leaders were willing to put into things like this - I know I would have enjoyed your demonstration at that age.

    The Iron filings align with the magnetic field lines, which are vectors and thus when 2 or more magnetic fields interact, they are added as such. Magnetic fields are defined in terms of the force that would act on a charged particle (the Lorentz force).

    I won't comment on the safety aspect - I'm not really qualified to do so.
  4. Mar 27, 2014 #3
    You are correct that the wires are getting hot due to the current being high. Unfortunately, to lower heat, you probably need to remove some of the power cells. I do not think anything will explode, but they may fail. I am not an expert either, but I don't think you will see anything serious occur.

    I think your demo is great, but I do believe it is important you stress these are electromagnets and explain how they differ from permanent magnets. The key to your demo though is in your explanation of Lens' Law and induction. Really drive home the fact that the phenomenon described by Lens is due to nature's need to eliminate change in magnetic flux. Make an analogy the kids can grasp that explains this sufficiently. I think with this elaboration (which isn't easy), you'll have a perfect demo.

    Good luck!
  5. Mar 27, 2014 #4
    Ok thanks thats great.... and I added one more item to the agenda, make a compass by floating the Alnico magnets on expanded polystyrene in tubs of water
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