Apr 7, 2011

New Physics teacher next term + story of almost electrocution

Look, an airplane.
We're getting a new physics teacher next term! The current temporary teacher we have is a really cool person.

We were doing electricity today, and he was telling us about the time he almost got electrocuted. He was in primary school, and just about to put wet clothing into the dryer (and this is those old dryers where the air cycles though, not a tumble dryer). He grabbed the handle and got shocked.

Once you grab something and get a strong current going through you, it's impossible to let go because your reflex action is to grip, and you just can't let go. That's why when you touch something that might be live, do it with the back of your hand so the reflex action doesn't make you grip onto the object until you die of electrocution.

He couldn't let go of the handle, so guess what he did? He ripped the handle off, and that broke the circuit. When his mum came back home the only thing she could say was "You broke my dryer! You broke my dryer!" She had her priorities straight, didn't she. The boy survived with nary a mark, but the dryer, the poor dryer!

He told us about a brave fella who worked with live wires with his left feet up in the air so the current goes through him to the Earth. If he had his left feel down on the ground, the current going through his heart would have killed him. Apparently cows do about the same thing. In a electrical storm, they stick their read ends up in the air towards where they think the lightning might come from, so the current goes to the Earth through their hind-legs. If they were facing the lightning, the current would go through their heart and kill them. (Ag people, bet you didn't know that. Dazzle your classmates with this useless piece of trivia)

He did an experiment with us to demonstrate the security fuse in most appliances and houses now. He set up a circuit and one section of it was very very fine wire, I'm talking about thinner than hair fine. He flipped on the switch and the light bulb lit up. That's what happens when everything is working properly.

He then used a lead to bypass the light bulb, and flipped on the switch. This time, the fine wires glowed orange, burned and broke. He touched the broken ends together and sparks flew. It was like a mini fireworks. Some parts of the wire kept on burning and melting after it broke, and they melted into tiny pebbles on the bench. Half the class gathered around and kept making it burn.

Is it just the children that have an unhealthy fascination with fire? Or is it everyone? There's a girl in my chemistry class that lights match after match and watches them burn. She once set up a whole row of matches with their heads lined up and lit one end, so the fire spread from one end to the other. I must say it did look spectacular. I heard that a friend built a bonfire using matches. I have guilty memories of burning things I'm not suppose to and watching the fire.


  1. wow, lots of interesting information here. I particularly liked the touching the handle with the back of your hand point. :D Thanks!

  2. He's a fun teacher, but the new Physics teacher is better at teaching. he could not control the class at all.