Physics Times 07.2019

(Kiana) #1


  1. Magnetic Moment (^) M:
    M m 2  
    Its unit is ampere metre^2.




  2. Magnetic Field
    It is also called as magentic flux density (or)




magnetic field vector ( )B.

Magnetic induction at a point in a magnetic field is
defined as force experienced by a unit north pole
placed at that point.


B F
m




S.I unit is tesla or weber / m^2
The magnetic field induction due to a pole of pole
strength m at a distance ‘d’ is given by B 0 =


2

0
4 d

m









  1. Torque on a Magnetic Dipole


In vector notation   M B


  


  1. Potential energy of a magnetic dipole


(^) U MBcos  M B 
The work done by an external agent in deflecting a
magnet from angular position  1 to an angular
position  2 with the field is given as
W    U U 2 U 1 MB(cos   1 cos ) 2



  1. Field of a Bar Magnet


(1) Axial line: (^02) 2 2
2
a 4 ( )
Md
B
d l


 
   
For a short bar magnet i.e., l d^2 ^2 ;
then Ba
0
3
2
4
M
d


 
 
 
(2) Equatorial line:
0
e 4 ( 2 2 3/ 2)
B M
d l




For a short bar magnet i.e., l d^2 ^2 ; then
Be =
0
4
 
  

^



  1. Magnetic Moment :




  1. Magnetic Field






  1. Torque on a Magnetic Dipole




  1. Potential energy of a magnetic dipole




  1. Field of a Bar Magnet


3

M
d
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