2: The Electron

Example number 2.1, Page number 18

In [9]:
#import modules
import math
from __future__ import division

#Variable declaration
E=2400;         #electric field intensity(V/m)
V=90;           #potential difference(V)
e=1.6*10**-19;       #the charge on electron(C)
m=9.12*10**-31;      #mass of electron(kg)

#Calculation
F=e*E;      #force on electron(N)
a=F/m;      #acceleration(m/s^2)  
KE=e*V;     #Kinetic Energy of particle(J) 
v=math.sqrt(2*KE/m);       #velocity of the electron(m/s)
v=v*10**-6;
v=math.ceil(v*10**2)/10**2;   #rounding off to 2 decimals

#Result
print "The force on electron is",F,"N"
print "Its acceleration is",round(a/1e+14,2),"*10**14 m/s^2"
print "The Kinetic Energy of particle is",KE,"J"
print "The velocity of the electron",v,"*10**6 m/s"
print "answers for acceleration and velocity given in the book varies due to rounding off errors"

The force on electron is 3.84e-16 N
Its acceleration is 4.21 *10**14 m/s^2
The Kinetic Energy of particle is 1.44e-17 J
The velocity of the electron 5.62 *10**6 m/s
answers for acceleration and velocity given in the book varies due to rounding off errors

Example number 2.2, Page number 18

In [13]:
#import modules
import math
from __future__ import division

#Variable declaration
V=900;      #potential difference(V)
B=0.01;       #uniform magnetic field(Wb/m^2)
em=1.76*10**11;       #value of e/m(C/kg)

#calculation
v=math.sqrt(2*em*V);        #linear velocity of electron(m/s)
R=v/(em*B);             #radius of the circular path(m) 
R=math.ceil(R*10**3)/10**3;   #rounding off to 3 decimals
v=v*10**-7;
v=math.ceil(v*10**2)/10**2;   #rounding off to 2 decimals

#Result
print "The linear velocity of electron is",v,"*10**7 m/s"
print "The radius of the circular path is",R,"m"

The linear velocity of electron is 1.78 *10**7 m/s
The radius of the circular path is 0.011 m

Example number 2.3, Page number 18

In [16]:
#import modules
import math
from __future__ import division

#Variable declaration
d=6*10**-3;       #distance between plates(m)
V=900;          #potential difference(V)
B=0.5;          #uniform magnetic field(Wb/m^2)
Q=1.6*10**-19;      #the charge on electron(C)
R=10.6*10**-2;      #circular track radius(m)

#calculation
v=V/(B*d);       #velocity(m/s)
m=R*Q*B/v;       #mass of particle(kg)

#Result
print "The mass of particle",round(m/1e-26,3),"*10**-26 kg"

The mass of particle 2.827 *10**-26 kg

Example number 2.4, Page number 19

In [2]:
#import modules
import math
from __future__ import division

#Variable declaration
V=6920;        #potential difference(V)
d=1.3*10**-2;      #distance between(m)
v=1.9*10**-4;      #velocity(m/s)
p=0.9*10**3;       #density of oil(kg/m^3)
n=1.81*10**-5;     #coefficient of viscosity(N-s/m^2)
g=9.81;          #accelaration due to gravity(m/s^2)

#calculation
a=math.sqrt((9*n*v)/(2*g*p));      #radius of the drop(m) 
E=V/d;         #electric field(V/m)
Q=4*math.pi*(a**3)*p*g/(3*E);      #value of charge on oil drop(C)

#Result
print "The radius of the drop is",round(a/1e-6,2),"micro m"
print "The value of charge on oil drop is",round(Q/1e-19,3),"*10^-19 C"
print "answers given in the book are wrong"

The radius of the drop is 1.32 micro m
The value of charge on oil drop is 1.612 *10^-19 C
answers given in the book are wrong