One day, Sheela wanted to ask some doubts on superconductors. She decided to approach prof.Govind in his laboratory. To her surprise, he was floating in mid-air defying gravity. She was astonished and ran out of words. She forgot why she'd come there and asked," Professor, How could you do that??!!!".
He jumped from mid-air and smiled at her. "Well, If a magician could do that, why can't I?"
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| "A magician performing anti-gravity trick" |
#1. Electrical resistance becomes zero.
#2. Magnetic lines of force are excluded from the material.
And these all happen for certain metals at low temperature only.Hope you might have heard about "Meissner effect".
When a superconductor is placed in a weak magnetic field, the field penetrates only a small part of the material(order of few micrometers). Just look at these pictures depicting Meissner effect", said Professor Govind.
"Meissner effect is a state of perfect diamagnetism in which, the magnetic field within the material of the superconductor is zero(B=0). This leads to the condition that the magnetic susceptibility is -1.
Whenever a magnet is brought near diamagnetic materials, they themselves become magnetized so as to oppose the external magnetic field. This is extreme in this case. You might be knowing that water is diamagnetic and this fact has helped scientists to levitate a frog applying a high magnetic field of "15 tesla", added him.
"That sounds interesting", exclaimed Sheela.
"Just watch what I'm doing. I'm pouring liquid nitrogen which boils at -196 degree Celsius so as to bring this metal piece to its superconduction state. It's always pleasure to watch how it levitates.
By now you could have understood the secret of anti-gravity and how I was floating in mid-air earlier", asked professor Govind.
"Hmm..That's true..and interesting too."
The magicians use cleverly placed steel bars
ReplyDeleteYes...Of course.It's just an illusion. They color the steel bars are the same color as the curtains behind, so that our eyes mis-perceive the trick!
ReplyDelete