Physics Times 07.2019

21. Magnetic Effects of Current

1.Biot - Savart’s Law

The field produced by the small element at P is

4 3

dB idl r

r





 

Here 40



 is the proportionality constant.

Where  is the permeability of the medium

107 1

4

 Hm





  

2. Magnetic field Due to a straight Wire

1.Biot - Savart’s Law

2. Magnetic field Due to a straight Wire

(^0) (sin sin )
4
B i
d
  

 
(I) For a wire of infinite length:
   90 
So, 40 [sin 90 sin 90 ]
i
B
d
  

 
2
i
d



(II) For a wire of semi-infinite length:
 90  and ^0 
So, 40 [sin 90 sin 0 ]
i
B
d
  

 