# Chapter 7 Electromagnetic theory¶

## Example 7.4 Page no 283¶

In :
#Given
u =4*10**-7*3.14                           #permeability ( free space ) in H/m
e =8.85*10**-12
H =1

#Calculation
import math
E=H* math.sqrt (u/e)

#Result
print"Magnitude of energy of plane wave is",round(E,2),"V/m"

Magnitude of energy of plane wave is 376.72 V/m


## Example 7.5 Page no 283¶

In :
#Given
ur =1                     #relative permeability
er =2
uo =(4*10**-7*3.14 )
eo =8.85*10**-12
Eo =5

#Calculation
import math
u=ur*uo
e=er*eo
Z= math.sqrt (u/e)
Ho=Eo/Z
v =1/(math.sqrt (u*e))

#Result
print"(i) Impedence of medium is",round(Z,2),"ohm"
print"(ii) Intensity of magnetic field is",round(Ho*10**2,3),"*10**-2 A/m"
print"(iii) Velocity of magnetic field is",round(v*10**-8,2),"m/s"

(i) Impedence of medium is 266.38 ohm
(ii) Intensity of magnetic field is 1.877 *10**-2 A/m
(iii) Velocity of magnetic field is 2.12 m/s


## Example 7.6 Page no 284¶

In :
#Given
f=3.0*10**11                          #frequency of wave in Hz
c=3.0*10**8
Eo =50

#Calculation
w=c/f
Bo=Eo/c

#Result
print"(i) Wavelength of wave is",w,"m"
print"(ii) Approx amplitude of oscillating magnetic field is",round(Bo*10**7,2)*10**-7,"T"

(i) Wavelength of wave is 0.001 m
(ii) Approx amplitude of oscillating magnetic field is 1.67e-07 T


## Example 7.7 Page no 284¶

In :
#Given
r =1.5*10**11                          #distance from sun to earth
P =3.8*10**26                          #power radiated by sun

#Calculation
import math
N=(P /(4*math.pi*(r**2) ))*60/4.2*10**4
N1= ceil (N)

#Result
print"Average solar energy is",round(N1*10**-8,0),"cal/cm2.min"

Average solar energy is 2.0 cal/cm2.min


## Example 7.8 Page no 284¶

In :
#Given
p=3.8*10**26                #watts
r=7*10**8                   #m

#Calculation
import math
N=p/(4*math.pi*((r)**2))

#Result
print"The magnitude of poynting vactor at the surface of the sun is",round(N*10**-7,3),"10**7","watt/m**2"

The magnitude of poynting vactor at the surface of the sun is 6.171 10**7 watt/m**2


## Example 7.9 Page no 285¶

In :
#Given
a=2
b=4.18*10**4
c=60.0
d=376.72

#Calculation
import math
E=a*b/c
E1=math.sqrt(E*d)
E2=E1/d
H=E1*math.sqrt(2)
H1=E2*math.sqrt(2)

#Result
print"The amplitudes of electrons is",round(H,0),"V/m"
print"The amplitudes of magnetic field is",round(H1,3),"Amp/m"

The amplitudes of electrons is 1025.0 V/m
The amplitudes of magnetic field is 2.72 Amp/m


## Example 7.10 Page no 285¶

In :
#Given
v =0.62                             #velocity factor of coaxial

#Calculation
Er =1/v**2

#Result
print"Dielecric constant of instulator is",round(Er,2)

Dielecric constant of instulator is 2.6