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Wednesday, 15 July 2009

the missing link in Electromagnetics


OK OK ... this post won't go down well with all ... it's dedicated and meant for the pure ... the absolutely pure theoritical physics lovers ... if you aren't one, you will find this post to be a deadly bore, and I forewarn you ... do NOT proceed ... I myself am having fears that many of you might even consider un-following my blog after reading this post ... but keeping my fingers crossed I embark ...

Ever wondered why gaps exist?

Bewildered?

Chill ... by gaps i refer not to literal gaps, but rather, gaps in theories ... make it ... er ... shortcomings ... in established theoritical concepts. Now say ... ever wondered why such shortcomings exist? If you did, then there's some pleasant news for you ... many great minds thought along the same lines, and unearthed loads of mind boggling new theories that helped "fill" the gaps.

Remember Mendeleef? The Mendeleef of the Periodic Table fame? Remember how he left gaps in his early Periodic Table model and confidently predicted the existence of elements that would conveniently "fill" the gaps in the table?
The same was done by Paul Dirac to predict the existence of positrons after he delved into the quantum-mechanical equation describing the behaviour of an electron, and hypothesised the existence of its anti-particle, and presto! the positron was postulated.

The common link between these ... incidents ... is NOT the fact that the truth was eventually uncovered ... but that they were uncovered following ... purely theoritical considerations. We call such considerations "thought experiments".

a detour:
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take this detour if you really want to, else continue from below :
Einstein's thought experiment:
One of the finest examples of a thought experiment was that of Albert Einstein which allowed him to establish his special theory of relativity later on. I read this in Simon Singh's brilliant book "The Big Bang" and am now trying to put it down in my own words. Galileo had postulated that any entity in an inertial frame (meaning a non accelerated frame) of reference would never be able to sense his motion ... in any way. So Einstein during one of his fits of wrambling :D wondered what would happen if one actually held a mirror in his hand and travelled at the velocity of light. He realised that according to common sense he would NOT see his reflection because the light rays would never actually leave his face if he was travelling at the speed of light itself ... got it? But that contradicted Galileo's postulate because then, one would be very much aware that he/she was indeed moving ... all the while sitting in an inertial frame. There was every possibility that Galileo's concept was WRONG, but Einstein had other explanations ... something that eventually materialsed into "the Special Theory of Relativity" ... coool ! what say? or perhaps a digusting waste of time ... :)
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So coming back to our topic ... there's is a certain beauty in all things that are natural, and so "gaps" in theories disgraces them, and stand out as blotches or dark marks. (There is in fact a theory that states "a simpler explanation is more likely than a complex one" ... called the Occam's razor theory) ... so the more "gaps" a theory has the more complexities it must bear to explain the gaps ... hence it loses credibility. It takes an intuitive mind to actually figure out how to fit the gaps in the existing theory by predicting the things that will fill in the gaps.

Electromagnetics is characterised by four unique variable aspects.
First, there is electric charge, which flows to produce electric current.
Electric current now creates magnetic fields.
Changing magnetic fields in a region generates voltage.

So we see how these four things are inter linked through their basic definitions.

Now, electric current is linked to voltage, not through a definition, but rather, by means of a device called a resistor. A resistor connects current with voltage by allowing only such an amount of current to flow though it when connected across a voltage so that the voltage:current ratio remains contant. Get it?

Similarly, a capacitor links charge and voltage, and an inductor links current and magnetic field. I hope you know how ... otherwise you wouldn't have read this far.
So we now have at hand ... FIVE links between the four variables.
However elementary mathematics states that four different things can be interlinked in 4c2 ways which amounts to six. Hence if theory is to be devoid of unruly gaps, then the theory must evolve to explain the one missing link OR some intuitive mind must predict the existence of somethng to fill in the "gap".

Going green? Drink some water and freshen up ... because this part gets quite hairy ... (if it hasn't already :) )

Leon Chua was the person who first conducted a thought experiment to fill this gap in electromagnetics and how! He realised that the missing link was that between "charge" and "magnetic fields" so there must ... theoritically ... exist something that linked the two. Chua did a lot of mathematics before actually ... shaping ... this elusive thing ... and postulated its manners and way of acting.

Chua realised that this device would need to link "charges" and "magnetic fields" ...so it must generate voltage from current .... only then would "charges" and "magnetic fields" be directly linked. Something which one has to get used to indeed!

Therefore, from purely theoritical considerations ... the "mem-ristor" was born in 1971.

And promptly disposed off, because it seemed pretty certain that such a thing could never exist.

Now however, we have enough reason to praise Chua's foresight because the memrisor has indeed become a reality.

What is it?

He he ... I'm yet to understand it perfectly, but as of now it appears to me to be a device that "remembers" the amount of charge that flowed through it, and hence calculates the "change" in current and the change in magnetic field giving rise to a certain voltage ... er ... that's all that I got ...
*grinning sheepishly*

But more than that what I wanted to actually stress upon is the way of thinking that led to this discovery ... how "thought experiments" actually work. Isn't the theory amazing?

PS: info gathered from the New Scientist website ... and assembled by myself
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