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An eddy current is caused by a moving magnetic field intersecting a conductor or vice-versa. The relative motion causes a circulating flow of electrons, or current, within the conductor. These circulating eddies of current create electromagnets with magnetic fields that oppose the change in the external magnetic field (see Lenz's law). The stronger the magnetic field, or greater the electrical conductivity of the conductor, the greater the currents developed and the greater the opposing force.
WHY WE TRY TO PREVENT IT:
Because of the tendency of eddy currents to oppose, eddy currents cause energy to be lost. More accurately, eddy currents transform more useful forms of energy, such as kinetic energy, into heat, which is generally much less useful.
EXTRA
Video of the eddy current:
http://video.google.com/videoplay?docid=1660843971041561797&q=neodymium&hl=en
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Here I found an animated cafe wall effect to understand it better
http://www.exploratorium.edu/exhibits/cafe_wall/cafe.html
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It creates a moving effect by magnifying the cafe wall illusion effect.
It does that by first creating many circles, each with many parts divided like a spiral-type shape.
THE CAFE WALL ILLUSION EFFECT:
The café wall illusion is an optical illusion, first described by Doctor Richard Gregory. He observed this curious effect in the tiles of the wall of a café at the bottom of St Michael's Hill, Bristol.
This optical illusion makes the parallel straight horizontal lines appear to be bent.
To construct the illusion, alternating light and dark "bricks" are laid in staggered rows. It is essential for the illusion that each "brick" is surrounded by a layer of "mortar" (the grey in the image). This should ideally be of a colour in between the dark and light colour of the "bricks".
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In the education of children there is nothing like alluring the interest and affection; otherwise you only make so many asses laden with books. ~Michel de Montaigne
Education is the ability to listen to almost anything without losing your temper or your self-confidence. ~Robert Frost
Children have to be educated, but they have also to be left to educate themselves. ~Abbé Dimnet, Art of Thinking, 1928
Learning, n. The kind of ignorance distinguishing the studious. ~Ambrose Bierce, The Devil's Dictionary
The modern world belongs to the half-educated, a rather difficult class, because they do not realize how little they know. ~William R. Inge
It is the mark of an educated mind to be able to entertain a thought without accepting it. ~Aristotle
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Please rate me too.
An Indian, a Pakistani and an American were being tested for lying.
The Indian said, "I think I can eat 30 kilos of rice in a day"
The lie detector machine immediately let out a loud BEEEP
"Ok, only 10"
and the green light came on..
The American said, "I think I can work 23 hours in a day"
BEEEEEEEEEP. "Ok only 12" *green light*
Paki said, "I think .." BEEEEP
Howz it? Please rate me!
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An Indian, Pakistani and a Bangladeshi were sitting in a bar, discussing.
The Pakistan said, "In my country we have so much sand that I can afford to do this." He immediately takes out a gun and shoots the glass bottle in front of him.
The Bangladeshi says, "In my country we have lots of drinks, so I can afford to do this." He takes out a gun and shoots the glasses of drinks that the Indian and Pakistani were drinking.
The Indian, infuriated, says, "In my country we have lots of Pakistanis and Bangladeshis, so I can afford to do this." And he shoots them both...
Howz it?
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Potassium-argon dating involves electron capture or positron decay of potassium-40 to argon-40. Potassium-40 has a half-life of 1.3 billion years, and so this method is applicable to the oldest rocks.
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Glass has a peculiar property - it allows infra red rays of shorter wavelengths (high temperature) to pass through it, but does not allow infra-red radiation of longer wavelengths (low temperature) to pass through it. Greenhouses use this in cold areas to conserve heat.
When an object is heated up by the shorter wavelength infra red rays(high temperature), it becomes hot and emits longer wavelength infra red rays (not as high temperature). Glass doesn't allow this to pass through and these radiations accumulated over time increase the temperature in the greenhouse.
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I also think the answer to master_purav's question should be B.
The nut would orbit the earth and I think bringing it closer to the earth and then bringing it to rest would cause it to fall on the earth.
The water boils I think... not sure.
Please rate me if you found the answer useful
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Elements are substances consisting of only one kind of substance and cannot be separated into simpler substances by physical and/or chemical methods.
Aluminium is used mainly in making airplane parts and household utensils.
Compounds are substances that cannot be broken down into simpler substances by physical methods
Metals are used for making alloys, utensils, electric wires, etc. since they are good conductors of electricity.
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