Serious issue on Fundamentals of Electromagnetic Induction
During the study of inductance of an inductor coil we consider
two type of inductor coil
1)
Ideal Inductor: - Which wire has zero resistance.
2) Real Inductor: - Which wire has some finite resistance.
During solving
circuits we say there is a potential difference between two end points of ideal inductor, even written
in books and sheets of so many coaching institute.
Prof Walter Lewin of MIT Physics department state that this is
wrong in their video lecture 20 (Lec 20 - MIT 8.02 Electricity and Magnetism_
Spring 2002, at 13 minute out of 51 minute, www.youtube.com/watch?v=UpO6t00bPb8)
Potential difference
between two end points of an ideal inductor is zero, not equal to
which is
written in our sheet.
·
It should be zero in case of ideal inductor
because Ideal inductor is made of superconductor and super conductor has zero
electrical resistance.
·
In case of real conductor would be
.
We should not apply Kirchhoff’s Voltage Rule during Solving LR
Circuit.
Whatever Equation we get by doing such two big mistakes is
mathematically correct so give correct answer. That is just goodness of
mathematics. But fundamentally we are wrong in doing so.
Ravendra Kumar
Ravendra Kumar
(RVN)
Yes i agree
ReplyDeleteRavinder! If u remember we met in a train from bandra to lucknow two days back. You had given me this link of yours.
ReplyDeleteA point was made by you that electric field inside a superconductor of resistance zero is zero and therefore potential drop across its length by the relation V = E*d is also zero.
The logic for making E as zero was given by you via relation J = sigma * E where sigma is infinite for superconductor.
Since sigma is infinite therefore E = J/sigma is zero.
But the fault in lovic here is that you assumed J to be a finite quantity. Finite/ infinite indeed is 0 but what is the logic behing taking J as finite.
On the contrary by the same relation of J =sigma* E, assuming E to be finite J comes out to be infinite for sigma as infinite. Now taking reverse E = infinite/infinite which is inderminate and not necessarily zero.
It also makes sense to assume latter because quite clearly for zero resistance even a small value of force (force from E) will continuosly increase the velocity of charges as there is no resistance to oppose. Therefore value of current also increases tremendously and therefore current density.
In this situation indeed potential difference between two points comes out to be zero even though E is non zero because there is no resistance to work against
If in circuit [Ideal Inductor connected to only Ideal Battery] there is no resistance then we know current is keep increasing linearly with time from zero but finite .
ReplyDeleteIf in circuit there is a resistor then current doesn't increases linearly, It will become finite after steady state
Inside inductor current is finite