# Chapter 15 Electromagnetic waves¶

## Example 15.1 Page no 836¶

In [7]:
#Given
e=8.854*10**-12                           #C**2/N/m**2
A=10**-4                                  #m**2
E=3*10**6                                 #V/ms

#Calculation
Id=e*A*E

#Result
print"Displacement current is", round(Id*10**9,1)*10**-9,"A"

Displacement current is 2.7e-09 A


## Example 15.2 Page no 836¶

In [10]:
#Given
Id=1                     #A
C=10.0**-6                      #F

#Calculation
V=Id/C

#Result
print"Instantaneous current is", V,"V/S"

Instantaneous current is 1000000.0 V/S


## Example 15.3 Page no 836¶

In [24]:
#Given
I=0.15                     #A
R=0.12                     #m
r=0.065                     #m
r1=0.15                   #m

#Calculation
import math
A=math.pi*R**2
u=4*math.pi*10**-7
B=(u*I*r)/(2*math.pi*R**2)
B1=(u*I)/(2*math.pi*r1)
Bmax=(u*I)/(2*math.pi*R)

#Result
print"(i) (a) Magnetic field on the axis is zero"
print"(b) Magnetic field at r=6.5 cm is",round(B*10**7,2)*10**-7 ,"T"
print"(c) Magnetic field at r=15 cm is", B1,"T"
print"(ii) Distance is", Bmax,"T"

(i) (a) Magnetic field on the axis is zero
(b) Magnetic field at r=6.5 cm is 1.35e-07 T
(c) Magnetic field at r=15 cm is 2e-07 T
(ii) Distance is 2.5e-07 T


## Example 15.5 Page no 837¶

In [29]:
#Given
r=0.05                      #m
E=10**12                     #V/m/s
e=8.854*10**-12

#Calculation
import math
Id=e*math.pi*r**2*E

#Result
print"Displacement current is", round(Id,4),"A"

Displacement current is 0.0695 A


## Example 15.7 Page no 846¶

In [41]:
#Given
E=100                            #v
c=3.0*10**8

#Calculation
import math
B=E/c
u=4.0*math.pi*10**-7
H=B/u
U=e*E**2

#Result
print"(i) Value of B is", round(B*10**7,2)*10**-7," T"
print"(ii) Value of H is",round(H,3),"A/m"
print"(iii) Energy density is",U,"J/m**3

(i) Value of B is 3.33e-07  T
(ii) Value of H is 0.265 A/m
(iii) Energy density is 8.854e-08


## Example 15.8 Page no 847¶

In [56]:
#Given
E0=8*10**-4                         #v
c=3.0*10**8
w=6*10**6

#Calculation
import math
B0=E0/c
f=w/(2.0*math.pi)
l=c/f

#Result
print"Wavelength of the wave is", round(l*10**-4,4),"m"
print"Frequency is",round(f*10**-6,3),"*10**10 Hz"

Wavelength of the wave is 0.0314 m
Frequency is 0.955 *10**10 Hz


## Example 15.9 Page no 847¶

In [59]:
#Given
E=6.3               #V/m
c=3.0*10**8

#Calculation
B=E/c

#Result
print"B=", B,"K^ Tesla"

B= 2.1e-08 K^ Tesla


## Example 15.10 Page no 847¶

In [65]:
#Given
f=18                         #W/cm**2
A=20                          #cm**2
t=30*60

#Calculation
U=f*A*t
P=U/c
F=P/t
P1=2*P
F1=P1/t

#Result
print"Average force exerted on the surface is", F1,"N"

Average force exerted on the surface is 2.4e-06 N


## Example 15.11 Page no 847¶

In [76]:
#Given
r=3.0                    #m
n=0.025
P=100                     #w
C=3*10**8

#Calculation
import math
A=4*math.pi*r**2
I=(n*P)/A
E0=math.sqrt((2*I)/(e*C))
B0=E0/C

#Result
print"Peak value of electric field is", round(E0,2),"V/m"
print"Peak value of magnetic field is",round(B0*10**8,2)*10**-8,"T"

Peak value of electric field is 4.08 V/m
Peak value of magnetic field is 1.36e-08 T