# Magnetic Properties¶

## Example number 4.1, Page number 119¶

In [2]:

#import module
import math
from __future__ import division

#Variable decleration
H=6.5*10**-4;    #magnetic field in T
M=1.4;     #field with iron

#Calculation
chi=M/H;
mew_r=1+chi;
mew_r=math.ceil(mew_r*10**2)/10**2;   #rounding off to 2 decimals

#Result
print("relative permeability of iron is",mew_r);

#answer given in the book is wrong

('relative permeability of iron is', 2154.85)


## Example number 4.2, Page number 119¶

In [3]:

#import module
import math
from __future__ import division

#Variable decleration
H=220;     #field in amp/m
M=3300;    #magnetisation in amp/m

#Calculation
chi=M/H;
mew_r=1+chi;

#Result
print("relative permeability is",mew_r);

('relative permeability is', 16.0)


## Example number 4.3, Page number 120 *¶

In [5]:

#import module
import math
from __future__ import division

#Variable decleration
r=5.29*10**-11;     #radius of orbit in m
B=2;   #applied field in Tesla
e=1.602*10**-19;   #charge of electron in coulomb
m=9.108*10**-31;    #mass of electron in kg

#Calculation
mew=(e**2)*(r**2)*B/(4*m);

#Result
print("magnetic moment in Am^2 is",mew);

('magnetic moment in Am^2 is', 3.94260574090909e-29)


## Example number 4.4, Page number 120¶

In [7]:

#import module
import math

#Variable decleration
chi=0.5*10**-5;    #susceptibility
H=10**6;      #field strength in amp/m

#Calculation
mew_0=4*math.pi*10**-7;
I=chi*H;
B=mew_0*(I+H);
B=math.ceil(B*10**3)/10**3;   #rounding off to 3 decimals

#Result
print("intensity of magnetisation in Amp/m is",I);
print("flux density in Weber/m^2 is",B);

('intensity of magnetisation in Amp/m is', 5.0)
('flux density in Weber/m^2 is', 1.257)


## Example number 4.5, Page number 120¶

In [10]:


#import module
import math
from __future__ import division

#Variable decleration
e=2.86;    #edge in armstrong
e=e*10**-10;        #edge in m
Is=1.76*10**6;    #magnetisation in amp/m
mewB=9.27*10**-24;   #1 bohr magneton in amp m^2

#Calculation
N=2/(e**3);    #density per m^3
mewbar=Is/N;
mew_bar=mewbar/mewB;
mew_bar=math.ceil(mew_bar*10**3)/10**3;   #rounding off to 3 decimals

#Result
print("average dipole moment in mewB is",mew_bar);

('average dipole moment in mewB is', 2.221)


## Example number 4.6, Page number 121 *¶

In [11]:

#import module
import math
from __future__ import division

#Variable decleration
H=10**6;    #magnetic field in amp/m
chi=1.5*10**-3;     #susceptibility

#Calculation
mew_0=4*math.pi*10**-7;
M=chi*H;
B=mew_0*(M+H);

#Result
print("magnetisation in Amp/m is",M);
print("flux density in Tesla is",B);

#answer for flux density given in the book is wrong

('magnetisation in Amp/m is', 1500.0)
('flux density in Tesla is', 1.258522017028071)


## Example number 4.7, Page number 121¶

In [13]:

#import module
import math
from __future__ import division

#Variable decleration
chi=3.7*10**-3;    #susceptibility
H=10**4;           #field strength in amp/m

#Calculation
mew_0=4*math.pi*10**-7;
M=chi*H;
B=mew_0*(M+H);
B=math.ceil(B*10**5)/10**5;   #rounding off to 5 decimals

#Result
print("magnetisation in Amp/m is",M);
print("flux density in Weber/m^2 is",B);

#answer for flux density given in the book is wrong

('magnetisation in Amp/m is', 37.0)
('flux density in Weber/m^2 is', 0.01262)


## Example number 4.8, Page number 121¶

In [14]:

#import module
import math
from __future__ import division

#Variable decleration
r=0.052*10**-9;     #radius of orbit in m
B=1;               #magnetic field in Wb/m^2
e=1.6*10**-19;      #charge of electron in coulomb
m=9.1*10**-31;      #mass of electron in kg

#Calculation
dmew=(e**2)*(r**2)*B/(4*m);

#Result
print("magnetic moment in Am^2 is",dmew);

#answer given in the book is wrong

('magnetic moment in Am^2 is', 1.901714285714286e-29)


## Example number 4.9, Page number 122¶

In [18]:

#import module
import math

#Variable decleration
chi=-0.5*10**-5;    #susceptibility
H=9.9*10**4;        #field strength in amp/m

#Calculation
mew_0=4*math.pi*10**-7;
I=chi*H;
B=mew_0*H*(1+chi);
I=math.ceil(I*10**4)/10**4;   #rounding off to 4 decimals
B=math.ceil(B*10**4)/10**4;   #rounding off to 4 decimals

#Result
print("intensity of magnetisation in Amp/m is",I);
print("flux density in Weber/m^2 is",B);

#answer for flux density given in the book is wrong

('intensity of magnetisation in Amp/m is', -0.495)
('flux density in Weber/m^2 is', 0.1245)


## Example number 4.10, Page number 122¶

In [22]:

#import module
import math
from __future__ import division

#Variable decleration
r=6.1*10**-11;     #radius of H atom in m
new=8.8*10**15;    #frequency in rev/sec
e=1.6*10**-19;

#Calculation
mew0=4*math.pi*10**-7;
i=e*new;
B=(mew0*i)/(2*r);
mew=i*math.pi*(r**2);
i=math.ceil(i*10**7)/10**7;   #rounding off to 7 decimals
B=math.ceil(B*10**3)/10**3;   #rounding off to 3 decimals

#Result
print("current in amp is",i);
print("magnetic induction in weber/m^2 is",B);
print("dipole moment in amp m^2 is",mew);

('current in amp is', 0.0014081)
('magnetic induction in weber/m^2 is', 14.503)
('dipole moment in amp m^2 is', 1.645933169972273e-23)


## Example number 4.11, Page number 123¶

In [24]:

#import module
import math
from __future__ import division

#Variable decleration
Is=1.96*10**6;     #saturation magnetisation in amp/m
a=3;             #cube edge of iron in armstrong
a=a*10**-10;    #cube edge of iron in m
mew_b=9.27*10**-24;     #bohr magneton in amp/m^2
n=2;    #number of atoms per unit cell

#Calculation
N=n/(a**3);
mewbar=Is/N;
mew_ab=mewbar/mew_b;
mew_ab=math.ceil(mew_ab*10**4)/10**4;   #rounding off to 4 decimals

#Result
print("average number of Bohr magnetons in bohr magneton per atom is",mew_ab);

('average number of Bohr magnetons in bohr magneton per atom is', 2.8544)


## Example number 4.12, Page number 123¶

In [28]:

#import module
import math
from __future__ import division

#Variable decleration
I=3000;     #magnetisation in amp/m
B=0.005;    #flux density in weber/m^2

#Calculation
mew0=4*math.pi*10**-7;
H=(B/mew0)-I;
mew_r=(I/H)+1;
H=math.ceil(H*10**3)/10**3;   #rounding off to 3 decimals
mew_r=math.ceil(mew_r*10**3)/10**3;   #rounding off to 3 decimals

#Result
print("magnetic force in amp/m is",H);
print("relative permeability is",mew_r);

#answer given in the book is wrong

('magnetic force in amp/m is', 978.874)
('relative permeability is', 4.065)


## Example number 4.13, Page number 124¶

In [31]:

#import module
import math
from __future__ import division

#Variable decleration
H=1800;          #magnetising field in amp/m
phi=3*10**-5;     #magnetic flux in weber
A=0.2;           #cross sectional area in cm^2

#Calculation
A=A*10**-4;       #cross sectional area in m^2
B=phi/A;
mew=B/H;
mew=math.ceil(mew*10**8)/10**8           #rounding off to 8 decimals

#Result
print("the permeability in Henry/m is",mew);

#answer given in the book is wron

('the permeability in Henry/m is', 0.00083334)


## Example number 4.14, Page number 124 **¶

In [36]:

#import module
import math
from __future__ import division

#Variable decleration
r=0.04;    #radius of circular loop in m
i=1000;    #current in mA
i=i*10**-3;    #current in amp
B=10**-3;    #magnetic flux density in Wb/m^2
theta=45;    #angle in degrees

#Calculation
A=math.pi*(r**2);
mew=i*A;
tow=i*B*math.cos(theta);
mew=math.ceil(mew*10**6)/10**6           #rounding off to 6 decimals

#Result
print("the magnetic dipole moment in amp m^2 is",mew);
print("the torque in Nm is",tow);

('the magnetic dipole moment in amp m^2 is', 0.005027)
('the torque in Nm is', 0.0005253219888177298)


## Example number 4.15, Page number 125¶

In [38]:

#import module
import math

#Variable decleration
A=100;   #area of hysteris loop in m^2
B=0.01;   #flux density in wb/m^2
H=40;    #magnetic field in amp/m
M=7650;   #atomic weight in kg/m^3

#Calculation
hl=A*B*H;

#Result
print("the hysterisis loss per cycle in J/m^3 is",hl);

('the hysterisis loss per cycle in J/m^3 is', 40.0)


## Example number 4.17, Page number 125¶

In [40]:

#import module
import math
from __future__ import division

#Variable decleration
hl=200;    #hysterisis loss per cycle in J/m^3
M=7650;    #atomic weight in kg/m^3
m=100;    #magnetisation cycles per second

#Calculation
hpl=hl*m;
pl=hpl/M;
pl=math.ceil(pl*10**4)/10**4           #rounding off to 4 decimals

#Result
print("hysterisis power loss per second in watt/m^3 is",hpl);
print("the power loss in watt/kg is",pl);

('hysterisis power loss per second in watt/m^3 is', 20000)
('the power loss in watt/kg is', 2.6144)

In [ ]: