I’d like to preface this post with a disclaimer – the following ideas, suggestions and demonstrations were not in response to a lack of technician support. Our technicians are great (and as I blog fairly discreetly, I’m not even saying this to get brownie points). But it’s amazing what you can demonstrate to kids with a piece of paper in physics, which is why an off-the-cuff demo turned into a lesson plan, which has now turned into a blog post.
This was the first I used – probably prompted by something I’ve seen elsewhere but I can’t place the source. A student unexpectedly challenged me about light and heavy objects falling at the same speed. While waiting for the guinea/feather apparatus I improvised. First I showed that two pieces of paper fell at different speeds when one was flat, the other crumpled into a ball. I then showed that if we removed the air resistance, even a flat piece of paper falls ‘quickly’ – the easiest way to do this was to place the paper above a book, then drop them together. As long as the paper does not overlap the edges of the book, they will still be touching as they hit the floor.
We all have students draw atoms as a nucleus made up of protons and neutrons, surrounded by orbiting electrons. I suspect I’m not the only one to add the caption ‘This diagram is a lie; discuss’ and sit back to watch the confusion blossom. But how about building the atoms out of classroom materials? If you use scrunched up balls of paper (mostly from the recycling bin of course) then they can actually start counting. Use different colours for each subatomic particle, and ask them to explain similarities and differences, or compare nuclides. You could even add treasury tags and build alpha particles to be emitted from the unstable nuclei. If you fancy it, this could be a rather more three-dimensional display than usual…
Students regularly struggle with the parallel (sorry) ideas of current and voltage in circuits. I have them make a circuit by standing in a loop, usually around the actual circuit laid out on the demo bench. Students are designated as cell and bulb (You could have them pin A4 circuit symbols to their clothes I guess, but the ideal would be netball bibs with added ink) and you will need one or several buckets, or washing up bowls.
Each bucket is passed around the circle, representing a moving charge. It gains electrical energy (in the form of scrunched up balls of paper) at the cell, and loses it at the bulb. I explain the energy is transformed at each point, it neither appears nor vanishes. It becomes obvious that we can increase how fast energy arrives at the device (students can easily mimic a buzzer or a motor but don’t get them to ‘flash’ as a bulb!) by increasing either the energy supplied per charge carrier at the cell, or by increasing the movement of charge carriers in the circuit. You can even link up with resistance by having the students in the loop, playing the part of the conducting wires, charge a ‘toll’ for passing the bucket.
Chain Reaction (nuclear fission)
This one is fun and the students will certainly remember it – but it should probably be used with caution. Give each student two pieces of scrunched up paper and have them stand up. Emphasize it is important to do this ‘practical’ slowly as otherwise the details are lost; ideally they should wait between each stage to appreciate the changes. Explain that they are atoms of nuclear fuels, uranium-235 or plutonium, which will decay if hit by a neutron. When they decay they will emit two neutrons and then sit down. They’ll need to wait for each stage, then choose a student and throw in some paper. They will choose their targets, and (slowly or quickly) 1 decaying atom will become 2, then 4, then 8, then 16… In practice, a few ‘neutrons’ will miss – this of course will really happen in a reactor! You can model the effect of control rods by having some students with no paper to throw.
Hope these inspire a few lesson starters or plenaries. I plan to demonstrate a few together as part of their revision, and then see if they can demonstrate a concept themselves, using paper.