The DJ on the radio this morning was asking people to ring in with experiences that happened while they were at school that have passed into legend. Unfortunately I heard it 5 minutes from the end of the show or I would have called in with this story:
When I was at school, many years ago, in Sunderland we had a physics teacher who had the classic Bobby Charlton comb over hair style obviously in a vain attempt to hide his baldness. One day while we were learning about electricity he decided to demonstrate the Van der Graaff generator. In case you don’t know the idea of the machine is that a constantly rotating belt builds up a static electric charge on the hollow metal sphere that surrounds one end of it. This will then discharge when a second metal sphere is brought into close proximity to it – the discharge is seen as a spark between the two spheres.
Anyway that’s how the experiment is supposed to work but there are other more fun ways of discharging the static charge. One such way is that if somebody stands on some insulated material like a block of polystyrene then touches the large dome the static will travel through them and be discharged to the first point it can find to earth itself – rather like getting a static shock when you touch a metal doorknob. So the teacher stands on the block and places one hand on the VDGG and then points to a Bunsen burner which has been turned on. The static charge leaps from the end of his finger and lights the Bunsen flame ta-da!!
Now as we all know there is another trick with static electricity – this is best demonstrated by rubbing a balloon against a jumper and holding it near to someone’s hair. The Van der Graaff had the same effect and his Bobby Charlton comb over started to stand on end. The whole class was in absolute hysterics as he fought to try and keep it down! However the demonstration needed both his hands to work so it was even more hysterical as he tried to continue! Happy Days!
I suspect that this couldn’t happen any more as the thought of someone putting himself up as a human lightning conductor would probably give the School’s Health & Safety person a even bigger shock than if he was to get on the end of the teachers electrically charged finger!