import math
# Variables
U_n = 1350. #mobility of electron in cm2/volt-sec
U_h = 480. #hole mobility in cm2/volt-sec
# Calculation
Sigma = 1.072*10**10 #density of electron hole pair per cc at 300°K for a pure silicon crystal
e = 1.6*10**(-19); #charge on the electron in C
Sigma_i = Sigma*e*(U_n+U_h); #Conductivity of pure silicon crystal
p_i = 1/(Sigma_i); #Resistivity of silicon crystal in Ohm-cm
P_i = p_i*10**(-2); #Resistivity of silicon crystal in Ohm-m
# Results
print 'Conductivity of pure silicon crystal = %.2e mho/cm'%Sigma_i
print 'Resistivity of silicon crystal = %.2e Ohm-m'%P_i
import math
# Variables
U = 1200; #electron mobility in cm2/Volt-sec
e = 1.6*10**(-19); #charge on the electron in C
# Calculation
n = 10**13; #concentration of phosphorus
sigma = U*e*n; #conductivity of crystal in mho/cm
p_i = 1/sigma; #resistivity of silicon wafer if all donor atom are active
# Results
print 'resistivity of silicon wafer if all donor atom are active is %.1e ohm-cm'%p_i
import math
# Variables
U_n = 3900 #mobility of electron in cm2/volt-sec
U_h = 1900 #hole mobility in cm2/volt-sec
n_i = 2.5*10**13; #concentration of electron
u_n = U_n*10**(-4); #mobility of electron in m2/volt-sec
u_h = U_h*10**(-4); #hole mobility in m2/volt-sec
e = 1.6*10**(-19); #charge on the electron in C
# Calculation
Sigma_i = n_i*e*(u_n+u_h)*10**6; #Conductivity
p_i = 1/(Sigma_i); #resistivity of intrinsic germanium rod
l = 1*10**(-2); #length of germanium rod in m
w = 1*10**(-3); #width of germanium rod in m
t = 1*10**(-3); #thick of germanium rod in m
A = w*t; #Area of cross section in m2
R = p_i*l/A; #Resistance of an intrinsic germanium rod in Ohm
# Results
print 'Resistance of an intrinsic germanium rod is %.2f K-Ohm'%(R/10**3)
import math
# Variables
N_a = 1.1*10**20; #acceptor density in atoms/m3
n_i = 2.5*10**19; #concentration of majority carrier per m3
# Calculation
n_p = (n_i**2)/N_a; #intrinsic density
R = n_p/n_i; #Ratio of n_p and n_i
# Results
print 'n_p/n_i = %.2f'%R
# rounding off error