Guericke’s electrical generator using a small jar and Lego. I used my ‘rough calloused hands’ to charge the glass (as Guericke did).
Since Easter I have been reading about electricity. I think it is the hardest topic to teach. Circuits are often frustrating: bulbs blow, cells run down, connecting wires have loose connections, one group takes all of the good wires…. And the rest is models, maths and abstract nouns.
A narrative route into electricity is a totally different approach, but I still wanted to have practical work. So I am making a Museum of Electrical History in my kitchen.
My exhibits are based on the texts for my book (so far, The Versorium Needle and Guericke’s Sulphur Sphere).
It seems reasonable to suppose that if the Earth has a fitting and appropriate attractive potency it will also have a potency of repelling things that might be dangerous or disagreeable to it.
Otto von Guericke 1663
Otto von Guericke was an extraordinary engineer. He is famous for inventing the vacuum pump (and disproving ‘nature abhors a vacuum’ – a pernicious error of the ancient Greek philosophers – Aristotle this time).
In 1654, Guericke used his pump to evacuate the air from his famous Magdeburg Hemispheres. These are two hollow hemispheres placed together and the air inside them pumped out. 16 horses were unable to pull the hemispheres apart – the most dramatic and famous physics demonstration of all time. Continue reading
A draft extract from my book using narrative to teach the big ideas of physics:
These are the utterly false and disgraceful tales of the writers.
William Gilbert, 1600
I will start my history of electricity with an utterly false and disgraceful lie: amber, when rubbed, will not attract dried basil.
The ancient Greek philosophers had a method for finding the truth. Observation played a part, but only observation of naturally occurring phenomena. Experiments did not count, because experiments are artificial. Observation combined with reason was the preferred method of finding the truth. This produced excellent mathematics but dodgy science. They claimed that amber would not attract dried basil, but did not test this claim. Continue reading
I don’t really mind which model for current anyone prefers – rope, hosepipe, cups with marbles etc. They all help at first, but leave you lost when you really start thinking.
Instead, I am writing a history of electricity in ten experiments. The first is whether rubbed amber will attract dried basil (I’ve checked it does), through static generators to dangling boys and twitching frogs’s legs.
The amber and basil controversy
My plan is to reproduce these experiments in my kitchen. I’ve made a very nice static generator from a jam-jar and Lego. I am now making a Leyden jar, which is where it starts to get dangerous. I won’t be flying a kite in a thunder storm and I think I may fail to make a high voltage evacuated Crooke’s tube. Will I have the stomach to try Galvani’s frog’s leg?
My mission is to describe the slow, difficult unravelling of our theories of electricity. The models don’t work, because electricity is so abstract. A narrative may help.
Throughout my 21 years of teaching, physics teachers have been in short supply. There have always been science departments with no physics specialist.
Statistics show the situation is getting worse. Continue reading