# Chapter 2 Electric field¶

## Example 2.1 Page no 39¶

In [2]:
#Given
m=10**-7                       #Kg
q=1.6*10**-19                  #C
g=9.8

#Calculation
E=(m*g)/q

#Result
print"Electric field strength required is", E

Electric field strenght required is 6.125e+12


## Example 2.2 Page no 39¶

In [6]:
#Given
m=10.0**-3                 #Kg
q=5*10**-6                 #C
u=20                       #m/s
E=2*10**5                  #N/C

#Calculation
F=q*E
a=-F/m
S=-u**2/(2.0*a)

#Result
print"Distance travelled is", S,"m"

Distance travelled is 0.2 m


## Example 2.3 Page no 39¶

In [28]:
#Given
E=2.55*10**4                       #V/m
a=1.26*10**3                        #Kg/m**4
g=9.81                               #m/s**2
e=1.6*10**-19

#Calculation
import math
q=12*e
Fe=q*E
r=((3*Fe)/(4.0*math.pi*a*g))**0.333

#Result
print"The radius of the drop is", round(r*10**4,5)*10**3,"*10**-4 mm"

The radius of the drop is 9.95 *10**-4 mm


## Example 2.4 Page no 39¶

In [41]:
#Given
m=80.0*10**-6                         #Kg
q=2*10**-8                           #C
E=20000                               #V/m
g=9.8

#Calculation
import math
a=(q*E)/(m*g)
a1=math.atan(a)*180/3.14
T=(q*E)/(math.sin(a1*3.14/180.0))

#Result
print"Tension in the thread of the pendulum is", round(T*10**4,1),"*10**-4 N"
print"Angle it make with the vertical is",round(a1,2),"Degree C"

Tension in the thread of the pendulum is 8.8 *10**-4 N
Angle it make with the vertical is 27.04 Degree C


## Example 2.5 Page no 40¶

In [50]:
#Given
q1=2.0*10**-7                    #C
q2=1.0*10**-7                    #C
r=10.0**-2                         #m
m=9*10**9

#Calculation
import math
E1=(m*q1)/r**2
E2=(m*q2)/r**2

#Result
print"Magnitude of field E1 is", E1*10**-7,"*10**7 N/C"
print"Magnitude of field E2 is", E2*10**-6,"*10**6 N/C"

Magnitude of field E1 is 1.8 *10**7 N/C
Magnitude of field E2 is 9.0 *10**6 N/C


## Example 2.6 Page no 40¶

In [60]:
#Given
q1=5.0*10**-19                           #c
q2=20*10**-19
r=2.0                                 #m

#Calculation
import math
x=-math.sqrt(q2/q1)
x1=math.sqrt(q2/(q1*3))

#Result
print"The point on the line joining is", round(x,1),"m and ",round(x1,1),"m"

The point on the line joining is -2.0 m and  1.2 m


## Example 2.7 Page no 40¶

In [71]:
#Given
r=0.2
m=9*10**9
qa=3*10**-6
q=1.5*10**-9

#Calculation
a=r/2.0
Ea=(m*qa)/a**2
Eb=(m*qa)/a**2
E=Ea+Eb
F=q*E

#Result
print"(a) Electric field at the mid point is", E*10**-6,"*10**6 N/C (along OB)"
print"(b) Force experienced by the test charge is",F*10**3,"*10**-3 N (along OA)"

(a) Electric field at the mid point is 5.4 *10**6 N/C (along OB)
(b) Force experienced by the test charge is 8.1 *10**-3 N (along OA)


## Example 2.8 Page no 40¶

In [82]:
#Given
qa=16*10**-6                          #c
qb=-9.0*10**-6                          #C
r=0.08                                #m

#Calculation
x=-(qa/qb)*r

#Result
print"Position of the point is", round(x,2),"m"

Position of the point is 0.14 m


## Example 2.9 Page no 41¶

In [33]:
#Given
m=9*10**9
qa=4*10**-6
r=2.0*10**-2
r1=10**-2
qb=2*10**-6

#Calculation
import math
Ea=(m*qa)/r**2
Eb=(m*qb)/r1**2
a=r1/r
E=math.sqrt(Ea**2+Eb**2+(2*Ea*Eb*a))
a11=Ea*(math.sin(60)*180/3.14)/(Ea+Eb*(math.cos(60)*180/3.14))

#Result
print"Position is", round(a11,2)

Position is 0.16


## Example 2.10 Page no 41¶

In [21]:
#Given
q=500*10**-6
r=0.1                   #m
d=0.2
m=9*10**9

#Calculation
p=q*r
a=r/2.0
R=d+a
E=(m*2*p*R)/((R**2-a**2)**2)

#Result
print"Electric dipole moment of the dipole is", p,"Cm"
print"Electric field due to dipole is",E*10**-7,"*10**7 N/C"

Electric dipole moment of the dipole is 5e-05 Cm
Electric field due to dipole is 6.25 *10**7 N/C


## Example 2.11 Page no 41¶

In [1]:
#Given
q=0.2*10**-12         #C
w=10**-8              #m
r=0.1                 #m
e=9*10**9

#Calculation
p=q*w
E=(e*2*p)/r**3

#Result
print"The electric field at an axical point at a distance of 10cm from there mid point is", E*10**8,"*10**-8 N/C"

The electric field at an axical point at a distance of 10cm from there mid point is 3.6 *10**-8 N/C


## Example 2.13 Page no 42¶

In [10]:
#Given
E=10.0**4
t=9*10**-26                        #Nm

#Calculation
import math
p=t/(E*math.sin(30*3.14/180.0))

#Result
print"Dipole moment of the dipole is", round(p*10**29,1),"*10**-19 Cm"

Dipole moment of the dipole is 1.8 *10**-19 Cm


## Example 2.17 Page no 43¶

In [15]:
#Given
p=-10**-7        #Cm
i=10**5

#Calculation
F=p*i

#Result
print"Force is given by", F,"N"
print"Torque is zero"

Force is given by -0.01 N
Torque is zero