# Chapter 7: Magnetic Materials¶

## example 7.1, Page No.252¶

In [3]:
#Horizontal component of magnetic Intensity
import math

#variable declaration
Bo=1.7*10**-5                 #in weber/m^2
meu_o=4*math.pi*10**-7        #permeability of free space in weber/amp-meter

#Calculations
H=Bo/meu_o                    #in A/m

#result
print("Horizontal component of magnetic filed intensity in A/m : %.1f"%H);

Horizontal component of magnetic filed intensity in A/m : 13.5


## exammple 7.2, Page No. 252¶

In [5]:
#Current through solenoid
import math
#variable Declaration
H=5*10**3                   #in Ampere-turns/m
l=10                        #in cm
l=l*10**-2                  #in meter
N=50                        #no. of turns
n=N/l                       #no. of turns per unit length

#Calculation
#Formula : H=n*i
i=H/n                       #in Ampere

#Result
print("Current should be sent through solenoid in Ampere : %.0f"%i)

Current should be sent through solenoid in Ampere : 10


## example 7.3, page no.252¶

In [8]:
#Magnetic moment of rod
import math
#variable declaration
meu_r=1000                           #relative permeability
n=5                                  #turns/cm
n=n*10**2                            #turns/meter
i=0.5                                #in Ampere
Volume=10**-4                        #in m^3

#calculation
I=(meu_r-1)*n*i                      #in Ampere
MagneticMoment=I*Volume              #in Ameter^2

#Result
print("Magnetic moment of the rod in Ampere-meter^2 : %.0f"%(math.ceil(MagneticMoment)))

Magnetic moment of the rod in Ampere-meter^2 : 25


## example 7.4, Page No.253¶

In [1]:
#Flux density magnetic intensity and permeability
import math
#variable Declaration
l=30                                         #in cm
l=l*10**-2                                   #in meter
A=1                                          #in cm^2
A=A*10**-4                                   #in meter^2
N=300                                        #turns of wire
i=0.032                                      #in Ampere
FI_B=2*10**-6                                #in weber
meu_o=4*math.pi*10**-7                       #permeability of free space in weber/amp-meter

#Calculations
B=FI_B/A                                     #in weber/meter^2
H=N*i/l                                      #in amp-turn/meter
meu=B/H                                      #in weber/Amp-meter
meu_r=meu/meu_o                              #Relative Permeability

#Result
print("Flux Density in weber/meter^2 :%.2f "%B)
print("\nmagnetic Intensity in amp-turn/meter : %.0f"%H)
print("\nPermeability in weber/amp-meter :%.2f *10^-4"%(meu*10**4))
print("\nRelative Permeability :%.3f "%meu_r)
#Answer of relative permeability is wrong in the book.

Flux Density in weber/meter^2 :0.02

magnetic Intensity in amp-turn/meter : 32

Permeability in weber/amp-meter :6.25 *10^-4

Relative Permeability :497.359


## example 7.5, Page No.253¶

In [18]:
#Relative Permeability
import math
#variable declaration
Xci_m=9.48*10**-9                            #usceptibility of medium(unitless)

#calculation
meu_r=1+Xci_m                                #relative permeability(unitless)

#result
print("Relative Permeability : %.2f * 10^-9\n"%(meu_r*10**9));
print("i.e, Relative Permeability is sligtly greater than 1.");

Relative Permeability : 1000000009.48 * 10^-9

i.e, Relative Permeability is sligtly greater than 1.


## example 7.6, page No.253¶

In [27]:
#Magnetising Force and material magnetisation
import math

#variable declarationm
n=10                       #turns/cm
n=n*10**2                  #turns/meter
i=2                        #in Ampere
B=1                        #in weber/meter^2
meu_o=4*math.pi*10**-7     #permeability of free space in weber/amp-meter

#Calculations
H=n*i                      #in amp-turn/meter
#Formula : B=meu_o*(H+I)
I=B/meu_o-H                #in amp-turn/meter
meu_r=B/(meu_o*H)          #relative permeability(unitless)

#result
print("Magnetising Force in amp-turn/meter :%.0f "%H)
print("\nMagn etisation of material in amp-turn/meter %.2f * 10^5:"%(math.ceil(I/10**3)/100))
print("\nRelative Permeability : %.0f"%(math.floor(meu_r)))

Magnetising Force in amp-turn/meter :2000

Magn etisation of material in amp-turn/meter 7.94 * 10^5:

Relative Permeability : 397