#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);
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