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Why magnetic field from a current carrying conductor obey inversesquare law? 
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#1
Nov1412, 11:46 AM

P: 22

I have read that the electric field from a point charge fall off as 1/(r*r) since it is analogous to
variation of intensity of radation from source (whose geometric proof depends on solidangle), similarily is there any geometric explanation why magnetic field in the stated case fall off as 1/(r*r). 


#2
Nov1412, 02:05 PM

P: 661

Bizarre "proof" that the static electric field is analoguous to a radiation... What about the gluon force? It increases over distance. What tells the previous reason in this case?
As for the static magnetic field... It cannot decrease as 1/R^2 because this would need a permanent current in an open wire. Either it's static, and then you need to close the circuit, and this loop creates a field as 1/R^3, or you have an antenna which accepts only AC current, and radiates an electromagnetic field, not a static magnetic one. So 1/R^2 exists only as a computation intermediate of static magnetic fields. 


#3
Nov1412, 02:07 PM

P: 1,969

The magnetic field of an infinite, linear conductor goes like 1/r where r is the distance from the wire (along the radius of a cylinder coaxial with the wire). Maybe you mean a different geometry of the current carrying conductor? 


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