11: Magnetic Properties

Example number 11.1, Page number 312

In [1]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;
B=0.2;     #magnetic induction(web/m**2)
H=500;        #magnetic field intensity(amp/m)

#Calculation
mewr=B/(mew0*H);      #relative permeability
chi=mewr-1;       #susceptibility

#Result
print "relative permeability is",round(mewr,1)
print "susceptibility is",round(chi,1)
print "answer in the book varies due to rounding off errors"

relative permeability is 318.3
susceptibility is 317.3
answer in the book varies due to rounding off errors

Example number 11.2, Page number 312

In [2]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;
chi=948*10**-11;       #susceptibility

#Calculation
mewr=1+chi;      #relative permeability
mew=mewr*mew0;       #absolute permeability

#Result
print "relative permeability is",mewr
print "absolute permeability is",round(mew*10**6,3),"*10**-6"

relative permeability is 1.00000000948
absolute permeability is 1.257 *10**-6

Example number 11.3, Page number 312

In [3]:
#importing modules
import math
from __future__ import division

#Variable declaration
H=6.5*10**-4;      #magnetizing force(amp/m)
M=1.4;       #magnetic field(T)

#Calculation
chi=M/H;    
mewr=1+chi;       #relative permeability

#Result
print "relative permeability is",int(mewr)
print "answer in the book is wrong"

relative permeability is 2154
answer in the book is wrong

Example number 11.4, Page number 312

In [4]:
#importing modules
import math
from __future__ import division

#Variable declaration
H=220;      #magnetizing force(amp/m)
M=3300;       #magnetic field(T)

#Calculation
chi=(M/H)+1;      #relative permeability

#Result
print "relative permeability is",int(chi)

relative permeability is 16

Example number 11.5, Page number 313

In [5]:
#importing modules
import math
from __future__ import division

#Variable declaration
H=1600;      #magnetizing force(amp/m)
phi=4*10**-4;     #flux(weber)
A=4*10**-4;     #area(m**2)

#Calculation
B=phi/A;
mew=B/H;      #permeability of rod(weber/amp.m)

#Result
print "permeability of rod is",mew*10**3,"*10**-3 weber/amp.m"

permeability of rod is 0.625 *10**-3 weber/amp.m

Example number 11.6, Page number 313

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

#Variable declaration
H=10**6;      #magnetizing force(amp/m)
mew0=4*math.pi*10**-7;
chi=1.5*10**-3;       #susceptibility

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

#Result
print "magnetisation of material is",M/10**3,"*10**3 A/m"
print "flux density is",round(B,3),"T"
print "answer in the book varies due to rounding off errors"

magnetisation of material is 1.5 *10**3 A/m
flux density is 1.259 T
answer in the book varies due to rounding off errors

Example number 11.7, Page number 313

In [7]:
#importing modules
import math
from __future__ import division

#Variable declaration
mew0=4*math.pi*10**-7;
phi=2*10**-6;     #flux(weber)
A=10**-4;     #area(m**2)
N=300;      #number of turns
l=30*10**-2;    #length(m)
i=0.032;     #current(ampere)

#Calculation
B=phi/A;       #flux density(weber/metre**2)
n=N/l;
H=n*i;        #magnetic intensity(amp-turn/metre)
mew=B/H;      #permeability of ring(weber/amp-metre)
mewr=mew/mew0;      #relative permeability
chi=mewr-1;      #magnetic susceptibility

#Result
print "flux density is",B*10**2,"*10**-2 weber/metre**2"
print "magnetic intensity is",int(H),"amp-turn/metre"
print "permeability of ring is",mew*10**7,"*10**-7 weber/amp-metre"
print "relative permeability is",round(mewr,1)
print "magnetic susceptibility is",int(chi)
print "answer in the book is wrong"

flux density is 2.0 *10**-2 weber/metre**2
magnetic intensity is 32 amp-turn/metre
permeability of ring is 6250.0 *10**-7 weber/amp-metre
relative permeability is 497.4
magnetic susceptibility is 496
answer in the book is wrong

Example number 11.8, Page number 316

In [9]:
#importing modules
import math
from __future__ import division

#Variable declaration
new=6.5*10**15;        #frequency(Hz)
r=0.54*10**-10;        #radius(m)
e=1.6*10**-19;     #charge(coulomb)

#Calculation
mew_m=e*new*math.pi*r**2;      #magnetic moment(A-m**2)

#Result
print "magnetic moment is",round(mew_m*10**24,2),"*10**-24 A-m**2"
print "answer in the book varies due to rounding off errors"

magnetic moment is 9.53 *10**-24 A-m**2
answer in the book varies due to rounding off errors

Example number 11.9, Page number 317

In [10]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;     #charge(coulomb)
m=9.1*10**-31;       #mass(kg)
h=6.64*10**-34;    #plank's constant(Js)

#Calculation
mewb=e*h/(4*math.pi*m);      #bohr's magneton(J/T)

#Result
print "bohr's magneton is",round(mewb*10**24,2),"*10**-24 J/T"

bohr's magneton is 9.29 *10**-24 J/T