# CHAPTER 2 : ELECTRONIC EMISSION¶

## Example 2.1: Page number 31¶

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#variable declaration

from math import exp
from math import pi

l=5.0;                        #length of tungsten filament in cm
d=0.01;                       #diameter of the filament in cm
T=2500.0;                     #operating temperature in K
A=60.2*pow(10,4);             #constant, depending upon the type of thermionic emitter, in amp/m²/K²
phi=4.517;                    #work function of emitter in eV

#Calculation
b=round(11600*phi,-1);                       #constant for a metal, in K
Js=round(A*T*T*exp(-b/T),-2);                #Emission current density in amp/m²
a=pi*(d/100)*(l/100);                        #Surface area of the cathode in m²
E_I=Js*a;                                     #Emission current in A

#Result
print("emission current =%.3f A"%E_I);

emission current =0.047 A


## Example 2.2:Page number 31¶

In :
from math import log

#Variable declaration
Js=0.1;                   #Emission current density in amp/cm²
A=60.2;                   #Constant depending upon the type of thermionic emitter, in amp/cm²/K²
T=1900.0;                 #Absolute temperature in K

#calculations
#Calculating b according to the formula Js=A*T²*exp(-b/T) for emission current density
b=-T*(log(Js/(A*T*T)));          #constant for emitter, in K
phi= round(b/11600,2);           # work function in eV

print ("Work function of the tungsten wire = %.2f eV"%phi);

if(phi==4.52):
print("Given sample is pure Tungsten");
elif(phi!=4.52 and phi>=2.63 and phi<=4.52):
print ("The sample is not pure Tungsten");

#Note : In the text book, the work function has been approximated to 3.56eV, but in the code it calculates as  3.52eV

Work function of the tungsten wire = 3.52 eV
The sample is not pure Tungsten

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