Chapter 16:Electric Potential

Ex16.1:pg-731

In [1]:
  import math   #Example16_1
 
  
#To find the magnitude of the electric field
v=12.0        #Units in V
d=5.0*10**-3        #units in Meters
e=v/d           #Units in V/meter
print "The magnitude of electric field is E=",round(e)," V/meters"

The magnitude of electric field is E= 2400.0  V/meters

Ex16.2:pg-731

In [2]:
  import math   #Example16_2
 
  
#To calculate the speed of the proton
q=1.6*10**-19      #Units in C
vab=45      #Units in V
m=1.67*10**-27        #Units in Kg
va=math.sqrt((2*q*vab)/m)       #Units in meters/sec
print "The speed of the proton is Vab=",round(va,2)," meters/sec"

The speed of the proton is Vab= 92858.79  meters/sec

Ex16.3:pg-733

In [3]:
  import math   #Example16_3
  
#To find the sped of an electron
e=1.6*10**-19      #Units in C
vab=45      #Units in V
m=9.11*10**-31        #Units in Kg
va=math.sqrt((2*e*vab)/m)       #Units in meters/sec
print "The speed of the electron is Vab=",round(va,2)," meters/sec"

The speed of the electron is Vab= 3975777.37  meters/sec

Ex16.4:pg-735

In [4]:
  import math   #Example16_4
 
  
  #To sketch the equipotentials and electric field lines near a charged metal object
print "Charged metal object have an equi potential volume so its surface is am equi potential volume\nBecause lines of force must be perpendiculat ro equipotential lines and surfaces."

Charged metal object have an equi potential volume so its surface is am equi potential volume
Because lines of force must be perpendiculat ro equipotential lines and surfaces.

Ex16.5:pg-735

In [5]:
  import math   #Example16_5
 
  
#To find the work done in carrying a proton and for an electron
q=1.6*10**-19   #Units in C
vab=9.0            #Units in V
work=q*vab        #Units in J
print "The work done in carrying proton is="
print work
print "Joules\n"
q=-1.6*10**-19   #Units in C
work=q*vab        #Units in J
print "The work done in carrying electron is="
print work
print "Joules\n"

The work done in carrying proton is=
1.44e-18
Joules

The work done in carrying electron is=
-1.44e-18
Joules

Ex16.6:pg-736

In [6]:
  import math   #Example16_6
  
  #To calculate the speed just befor it strikes it
va=8*10**6         #Units in meters/sec
q=1.6*10**-19         #Units in C
m=1.67*10**-27        #Units in Kg
vab=20000   #Units in V
vb=math.sqrt(va**2-((2*q*vab)/m))        #Units in meters/sec
print "The speed of proton before it strikes is Vb=",round(vb,1)," meters/sec"

The speed of proton before it strikes is Vb= 7756781.9  meters/sec

Ex16.7:pg-737

In [7]:
  import math   #Example16_7
 
  
  #To calculate the minimum value of Vab needed
print "Since each proton has a minimum energy of 13.6 eV and a charge of 1.602*10**-19 C\n The required potential difference is=13.6 eV"

Since each proton has a minimum energy of 13.6 eV and a charge of 1.602*10**-19 C
 The required potential difference is=13.6 eV

Ex16.8:pg-737

In [8]:
  import math   #Example16_8
  
  #To find out the speed of the proton
k=9*10**9         #Units in N meter**2/C**2
q=5*10.0**-6   #Units in C
r=0.5         #Units in meters
v1=(k*q)/r     #Units in V
q=1.6*10**-19           #Units in V
m=1.672*10**-27           #Units in Kg
v=math.sqrt((v1*q*2)/m)     #Units in V
print "The speed of electron is v=",round(v,2)," meters/sec"

The speed of electron is v= 4150286.78  meters/sec

Ex16.9:pg-739

In [9]:
  import math   #Example16_9
 
  
  #To compute the absolute potential at B
k=9*10**9         #Units in N meter**2/C**2
q=5*10.0**-8   #Units in C
r=0.1         #Units in meters
v1=(k*q)/r     #Units in V
q=8*10**-8   #Units in C
r=0.1         #Units in meters
v2=(k*q)/r     #Units in V
q=40*10**-8   #Units in C
r=0.2         #Units in meters
v3=-(k*q)/r     #Units in V
vb=v1+v2+v3            #Units in V        
print "Due to 5*10**-8 C V1=",round(v1)," V\nDue to 8*10**-8 C V2=",round(v2)," V\nDue to 40*10**-8 C V3=",round(v3)," V\n Absolute potential at B is Vb=",round(vb)," V"
      

Due to 5*10**-8 C V1= 4500.0  V
Due to 8*10**-8 C V2= 7200.0  V
Due to 40*10**-8 C V3= -18000.0  V
 Absolute potential at B is Vb= -6300.0  V

Ex16.10:pg-739

In [10]:
  import math   #Example16_10
 
  
  #To find the absolute potential and how much energy is needed to pull the electrons from atom
k=9*10**9         #Units in N meter**2/C**2
q=1.6*10**-19   #Units in C
r=5.3*10**-11         #Units in meters
v=(k*q)/r     #Units in V
print "The absolute potential is V=",round(v,1)," V\n"
Vinfinity=0              #Units in V
deltaV=Vinfinity-v           #Units in V
work=-q*deltaV             #Units in J
print "The energy that is required is W="
print round(work,20),"J"  

The absolute potential is V= 27.2  V

The energy that is required is W=
4.35e-18 J