Katie is a newly qualified teacher in a school where she is the only physics specialist. She is used to learning from her own mistakes so she didn’t let a broken Van der Graaff generator hold back her lesson on electrostatics
Year 10 Scheme of Work: Electrostatics. In my head flashed images of the perfect lesson, the sort you see in photos with a crowd of engaged students laughing with delight as their classmates’ hair stands on end thanks to the Van De Graaff Generator.
There was one problem – the school Van De Graaff was awaiting repair.
It didn’t matter. I had seen an inspiring demonstration of electrostatics at the IOP NQT Conference in July (Visualising Electric Fields and the Triboelectric Series). It involved a giant balloon, a foot pump and some polystyrene balls.We’d loved it. It had completely engaged the whole room, and the explanation was clear and effortless. No Van De Graaff? No problem! I would recreate this masterpiece.
I would simply purchase a giant, clear balloon, fill it with beads, pump it up and, voila, my students would understand that, by rubbing this giant balloon on my head, a transfer of electrons would charge the surface of the balloon and attract the balls inside. This could then be moved a step further by passing the balloon around the room, hence causing a movement of charge, thus representing ‘current’ – exactly as we had seen in London.
How it actually went:
I hadn’t considered the size of the balloon needed (I just knew that it needed to be big!), the quantity of balls to fill it with or how I would inflate it. In the end, I bought the biggest balloon I could from an online auction site, grabbed a carrier bag full of balls from the old bean-bag in the back of my garage and hassled my wonderfully accommodating lab technician to borrow a foot pump from the PE department.
My bright, top-set Year 10s were delighted by the demonstration. It engaged them, initiated questions that really probed the physics of what was happening and led to an effective and memorable lesson. Thankfully, studying triple science meant they had covered atomic structure in their Chemistry classes and easily picked up the concept of transfer of electrons and attraction of opposing charges. In a single lesson we covered the basics of electrostatics, its applications and the associated dangers. We even managed a plenary with the students making a video explaining the physics involved in the demonstration.
Well, not quite. I hadn’t considered the following:
– Inflating a 3ft balloon takes considerable effort. To be precise: an entire 45min lunch break, three colleagues and a foot pump. Watch out for the lactic acid build up…
– A 3ft balloon really is enormous.The logistics of moving it, inflated, along the narrow corridors of my school without incident was challenging, to say the least. Should you wish to recreate this demonstration, may I suggest you don’t attempt to shift it during lesson changeover when the corridors are packed with students who feel compelled to reach out and touch things.
– Your class will be suitably distracted by the presence of a giant balloon, and will therefore disregard your planned starter and any attempt at theory before your demonstration. Be prepared, therefore, to launch straight into the topic in the hope that they’ll just catch on.
– Trying to illustrate the electrostatic effect using teenagers’ hair is a doomed undertaking. Copious amounts of hairspray and/or styling product (both the boys and the girls) will render any sort of electrostatic charge impossible.
– It therefore follows that self-ridicule is the only option for effective demonstration of the effect on hair. Cue repeated requests such as: “Can we take a picture, Miss?”
– If you conduct a giant balloon investigation during period 1, and choose not to deflate the balloon in the vague notion that you might use it again, be prepared to teach the basics of electrostatics to every other class passing through your laboratory for the rest of the day. The intrigue associated with a 3ft balloon ‘hidden’ on the corner of your desk is simply too tempting for a class of year 7s who should be learning about cells.
– Should the giant balloon be accidentally popped by the cleaner, the resulting distribution of polystyrene balls will take over a term to clear up completely, if at all.
The naivety of an NQT:
Imagine my delight when electrostatics appeared a week later on the Scheme of Work, this time for my Year 11s studying for their additional science GCSE. Hooray, I thought! I could just recreate my previous lesson with minimal planning – an NQT’s dream! I had, however, overlooked that fact that this class hadn’t yet covered atomic structure, had no idea about electrons orbiting atoms and how these may be transferred by friction. They hadn’t covered attraction/opposition of charges and didn’t recall their KS3 knowledge of electricity.
Where my previous lesson’s demonstration had triggered an engaging Q&A session, for this class my questions were met with a resounding silence. It was one of those swan-like moments: calm on the exterior, paddling like mad under the water as I quickly re-thought what I was doing and how to ensure the class understood the premise.
What I learnt:
Thankfully, in both instances, the lesson was a success with plenaries confirming the students’ understanding of what they had learnt. However, my assumptions about the level of my Year 11’s existing knowledge nearly caused my second lesson to de-rail. As yet, I haven’t taught the full Scheme of Work used by my school and so it is easy to jump to conclusions that students have covered material which they may not have done.
Equally, assuming that my double-award students would have the same ability to grasp concepts as my top-set triple science students was a basic mistake. My Assessment for Learning techniques are improving as my NQT year progresses. Experiences such as this have highlighted the importance of establishing prior understanding of the students before launching into a new topic. Likewise, adapting my lessons to the ability of the group (whilst using the same demonstrations and principles) is an essential skill.
And the consequence was….
I am pleased to say that since my efforts – and despite the repair of the Van De Graaff – a number of colleagues have used the balloon demonstration in their classes. We have found that 1½ foot balloons are much more appropriate!
Links to related IOP resources
Key Stage 3
Key Stage 5
All Key Stages