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Motor on QI

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Motor on QI

Old 5th May 2012, 09:26
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Motor on QI

On the BBC panel game QI last night (4th May) the contestants built electric motors, (or at least spinning rotors) using the sole components of ; a short length of wire, an AA battery, a large woodscrew, and a small round magnet.

I've tried it myself, and it really works - but how?

The screw always rotates in the same direction, and is self starting. The wire in contact with the magnet is clearly acting as a commutator, and the field lines produced by the permanent magnet and the current passing through the screw must provide the motive power, but I can't see how.

Try it yourself - place the magnet on the head of the screw, suspend the screw point uppermost from one end of the battery (you need a powerful magnet, about the same size as the screw head), then use the wire to connect the other end of the battery to the side of the magnet.

Good luck.
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Old 5th May 2012, 11:36
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See Fleming's right-hand rule.
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Old 5th May 2012, 11:39
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Shouldn't that be his Left Hand rule for motors? I thought the Right Hand rule was for generators.
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Old 5th May 2012, 12:23
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Construction and explanation here
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Old 5th May 2012, 12:26
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The simplest motor of the world. [VIDEO]
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Old 5th May 2012, 13:16
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Shouldn't that be his Left Hand rule
How sinister

I was dredging the grey matter from 33 years ago so forgive my error. In any case, does it not go in the opposite direction south of the equator
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Old 5th May 2012, 13:32
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While you are at puzzles anyway, would anybody help me explain a friend why planes flying against the rotating of the Earth have to fly forward at all - he claims they could get off and stay up there until the Earth turns the destination right below them.
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Old 5th May 2012, 13:37
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could get off and stay up there until the Earth turns the destination right below them
If they could do 1000mph (approx, at the equator) they would. They would be doing 1000 mph relative to the earth's surface while the earth was spinning at the same speed the other way - i.e. the plane would be standing still relative to an observer out in space.

Speed would need to be less at different latitudes.

Cheers
UFO
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Old 5th May 2012, 14:07
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Actually, thinking about it, I don't believe it is Fleming's left or right hand rule, but actually Maxwell's corkscrew rule that makes it work.

Incidentally, there's no need to use a screw, a small symmetrical Yale type key works well. The best visual effect I've found is to use a large keyring with a small ball-bearing on top to reduce friction.
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Old 5th May 2012, 14:18
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Corkscrews are sadly becoming a thing of the past. I'm with the Maitre D' on this i.e. personally, I blame the French.
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Old 5th May 2012, 14:53
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Yer, as well as the electric light bulb we also invented the electric motor, twere a chap called Faraday wot done it.
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Old 5th May 2012, 15:13
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Originally Posted by probes View Post
While you are at puzzles anyway, would anybody help me explain a friend why planes flying against the rotating of the Earth have to fly forward at all - he claims they could get off and stay up there until the Earth turns the destination right below them.
Because planes fly against the air, and the air is generally following the rotation of the earth. It doesn't do so perfectly, of course, and when it doesn't, that's what we call "wind". If planes went above the atmosphere, as satellites do, that would be a different matter entirely.
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Old 5th May 2012, 15:15
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Faraday

The bloke who invented the cage as well?

"There were lions and tigers and camels
And old ale and sandwiches too"

(Just seeking for further amusement we paid and went in at the zoo)
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Old 5th May 2012, 15:26
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While you are at puzzles anyway, would anybody help me explain a friend why planes flying against the rotating of the Earth have to fly forward at all - he claims they could get off and stay up there until the Earth turns the destination right below them.
How big a conveyor belt would he need to try it, can try to knock one up out of wood, fairy liquid bottles and sticky-back plastic tomorrow......
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Old 5th May 2012, 15:43
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How big a conveyor belt would he need to try it, can try to knock one up out of wood, fairy liquid bottles and sticky-back plastic tomorrow......
any chance of a tracy island too ?
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Old 5th May 2012, 15:48
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Nope, one only does the impossible. Miracles are extra
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Old 5th May 2012, 16:10
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but actually Maxwell's corkscrew rule that makes it work
Touche!
Actually it's the magnetic field that makes it turn, and you could call that Marjorie or Derrick and it would still work.
While you are at puzzles anyway, would anybody help me explain a friend why planes flying against the rotating of the Earth have to fly forward at all - he claims they could get off and stay up there until the Earth turns the destination right below them.
has he tried jumping into the air to see how much the earth turns before he Lands?
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Old 5th May 2012, 16:18
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I don't get it. Desert Dingo's Video above says "Build a Simple Electric Motor in 5 minutes. Why is it a 17 and a half minute video?
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Old 5th May 2012, 16:37
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the rotating of the Earth


Question: in order for it to rotate, does the Elephant have to lie on his back and sort of juggle with his feet ? If not and the Elephant remains upright, I don't see how it can rotate at all.
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Old 5th May 2012, 16:41
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Don't be silly, OFSO, eni fule nos that the earth rotates because it is on the back of 4 elephants walking in a circle on the back of a giant turtle.
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