attain constant value for any value of H. Apart from it, it is also apparent from figure and that the variation of permeability with H is almost similar to that of susceptibility cm except that its rate of decrease is slower at high values of H.
3. The magnetic lines of forces are strongly attracted by ferromagnetic materials.
Q.4 Discuss Langevin’s theory of Diamagnetism. Show that the diamagnetic susceptibility is negative and independent of temperature and field strength.
(AKTU. 2004 - 05, 06-07)
Related
Questions -
Q. Describe Langevin’s theory of
Diamagnetism. Show that the magnetic susceptibility is independent of
temperature. (AKTU. 2004 - 05)
Q. Show that the diamagnetic susceptibility
is negative and is independent of temperature. (AKTU. 2006-07)
Q. Show that the magnetic
susceptibility of a diamagnetic material is negative and independent of
temperature. (AKTU. 2008-09)
Ans. Langevin’s Theory of Diamagnetism: -
In diamagnetic substances, the vector sum
of all magnetic moments due to oppositely paired current loops is zero. When an
external magnetic field is applied to such atom, the electronic orbit exhibit
precessional motion about the direction of the applied filed. This precession
is known as Larmor precession. Thus the applied magnetic filed causes an
increase or decrease in the angular velocity of the electrons depending upon
their direction of motion.
Let an electron revolving in a
circular orbit of radius r with angular frequency w0. The centripetal force acting on the electron Fc = mw02r = mv02/r
Where v0 is the speed of electron in orbit, m is the
mass of the electron.
If an uniform external magnetic
field is applied perpendicular to the plane of orbit then an additional
magnetic force is acting on electron, which is
Let (x, y,
z) be the coordinates of any point on an orbit of radius r, then
r2 = x2 + y2 + z2
If field B is
along Z- axis then
