Chapter 11: Cathode Ray Oscilloscope

Example 11.2,Page number 532

In [11]:
#Variable declaration
E=120                  #electric field(V/m)              
B=5*10**-5             #magnetic field(T) 
q=1.6*10**-19          #charge on electron(C)
u=10**6                #velocity of electron(m/s)
m=9.1*10**-31          #mass of electron(Kg) 
a=9.81                 #acceleration of gravitation(m/s^2)

#Calculations
#Part a
fe=q*E                #force on electron due to electric field(N)

#Part
fm=B*q*u             #force on electron due to magnetic field(N)

#Part c
fg=m*a               #force on electron due to gravitational field(N)

#Results
print"force on electron due to electric field is",fe,"N"
print"force on electron due to magnetic field is",fm,"N"
print"force on electron due to gravitational field is",fg,"N"

force on electron due to electric field is 1.92e-17 N
force on electron due to magnetic field is 8e-18 N
force on electron due to gravitational field is 8.9271e-30 N

Example 11.3,Page number 532

In [7]:
import math

#Variable declaration
T1=1200.                         #temperature(k)
T2=1000.                         #temperature(k)
Ww=1.2*10**5                     #work function(eV)
k=8.62
Ie1=200                         #emission current density
T3=1500.                        #temperature(k)

#Calculations
Ie2=Ie1*(T2/T1)**2*math.exp(-(Ww/k)*((1/T2)-(1/T1)))             #current density(mA/cm^2) at 1000k
Ie3=Ie1*(T3/T1)**2*math.exp(-(Ww/k)*((1/T3)-(1/T1)))             #current density(mA/cm^2) at 1000k

#Results
print"current density at 1000 k is",round(Ie2,2),"mA/cm^2"
print"current density at 1500 k is",round(Ie3,2),"mA/cm^2"

current density at 1000 k is 13.65 mA/cm^2
current density at 1500 k is 3180.49 mA/cm^2

Example 11.4,Page number 533

In [1]:
import math

#Variable declaration
Ls=40                     #distance from screen(m)
d=1.5                     #distance between plates(cm)
Va=1200                   #accelerating potential(V) 
L=3                       #length of CRT(m)
e=1.6*10**-19             #charge on electron(C)
m=9.1*10**-31             #mass of electron(Kg) 
Y=4*10**-2                #vertical deflection(V)

#Calculations
#Part a
U=math.sqrt((2*e*Va)/m)   #velocity of electron upon striking screen(m/s)

#Part
Vd=(2*d*Va*Y)/(L*Ls)      #deflecting voltage(V)

#Part c
Vdmax=(m*d**2*U**2)/(e*L**2)   #maximum allowable deflection(V)

#Results
print"velocity of electron upon stricking the screen is",round((U/1E+7),3),"*10^7 m/s"
print"deflecting voltage is",round(Vd/1E-2),"V"
print"maximum allowable deflection is",Vdmax,"V"

velocity of electron upon stricking the screen is 2.054 *10^7 m/s
deflecting voltage is 120.0 V
maximum allowable deflection is 600.0 V