# 14: Magnetism¶

## Example number 1, Page number 420¶

In [6]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;     #permeability of vacuum
H=10**12;                  #magnetic field intensity(A/m)
chi=20*10**-3;             #susceptibility

#Calculations
M=chi*H;                   #magnetisation(A/m)
B=mew0*(M+H);              #flux density(T)

#Result
print "magnetisation is",int(M/10**9),"*10**9 A/m"
print "flux density is",round(B/10**6,4),"*10**6 T"
print "answer for flux density given in the book is wrong"

magnetisation is 20 *10**9 A/m
flux density is 1.2818 *10**6 T
answer for flux density given in the book is wrong


## Example number 2, Page number 420¶

In [11]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;     #permeability of vacuum
H=10**2;                  #magnetic field intensity(A/m)
B=0.0224;                  #flux density(T)

#Calculations
M=(B/mew0)-H;              #magnetisation(A/m)

#Result
print "magnetisation is",int(M),"A/m"
print "answer for magnetisation given in the book is wrong"

magnetisation is 17725 A/m
answer for magnetisation given in the book is wrong


## Example number 3, Page number 421¶

In [13]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;             #charge(coulomb)
B=3;                       #flux density(T)
m=9.1*10**-31;             #mass(kg)

#Calculations
mew=B*e**2*r**2/(4*m);     #change in magnetic moment(Am**2)

#Result
print "change in magnetic moment is",round(mew*10**29,2),"*10**-29 Am**2"

change in magnetic moment is 5.27 *10**-29 Am**2


## Example number 4, Page number 421¶

In [15]:
#importing modules
import math
from __future__ import division

#Variable declaration
T1=200;          #temperature(K)
T2=300;          #temperature(K)
chi1=1.2*10**-4; #susceptibility

#Calculations
chi2=T1*chi1/T2;    #susceptibility

#Result
print "susceptibility is",chi2*10**4,"*10**-4"

susceptibility is 0.8 *10**-4


## Example number 5, Page number 422¶

In [18]:
#importing modules
import math
from __future__ import division

#Variable declaration
H=10**5;                  #magnetic field intensity(A/m)
chi=3.6*10**-3;            #susceptibility

#Calculations
M=chi*H;                   #paramagnetisation(A/m)

#Result
print "paramagnetisation is",M/10**2,"*10**2 A/m"

paramagnetisation is 3.6 *10**2 A/m


## Example number 6, Page number 422¶

In [21]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;     #permeability of vacuum
mewB=9.27*10**-24;
rho=8906;                  #density(kg/m**3)
W=58.7;                    #atomic weight

#Calculations
mewM=0.61*mewB;            #magnetic moment(Am**2)
B=rho*N*mew0*mewM/W;       #saturation magnetic induction(T)

#Result
print "magnetic moment is",round(mewM*10**24,3),"*10**-24 Am**2"
print "saturation magnetic induction is",round(B*10**4,1),"*10**-4 T"

magnetic moment is 5.655 *10**-24 Am**2
saturation magnetic induction is 6.5 *10**-4 T


## Example number 7, Page number 423¶

In [23]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;     #permeability of vacuum
e=1.6*10**-19;             #charge(coulomb)
m=9.1*10**-31;             #mass(kg)

diamagnetic susceptibility is -8.249 *10**-8