In [1]:

```
import numpy
import math
#Variable declaration
e = 1.6e-019; # Energy equivalent of 1 eV, J
k = 1.38e-023; # Boltzmann constant, J/K
T = 293; # Room temperature, K
#Calculations&Results
dE = [0.10, 1.0, 10.0]; # Energies above the valence band, eV
F_FD = numpy.zeros(3);
for i in range(0,3):
F_FD[i] = 1/(math.exp(dE[i]*e/(k*T)) + 1);
print "For E - E_F = %4.2f eV, F_FD = %4.2e"%(dE[i], F_FD[i])
```

In [2]:

```
#Variable declaration
e = 1.6e-019; # Energy equivalent of 1 eV, J
rho = 5.92e-008; # Resistivity of the zinc at room temperature, ohm-m
B = 0.25; # Magnetic field applied perpendicular to the strip, T
x = 10.0e-002; # Length of the zinc strip, m
y = 2.0e-002; # Width of the zinc strip, m
V = 20e-003; # Potential difference applied across the strip, V
I = 0.400; # Current through the strip, A
V_H = 0.56e-006; # Hall voltage that appeared across the strip, V
#Calculations
z = rho*x*I/(y*V); # Thickness of the strip, m
n = I*B/(e*V_H*z); # Number density of the charge carriers, per metre cube
#Results
print "The thickness of the zinc strip = %4.2e m"%z
print "The number density of the charge carriers = %4.2e per metre cube"%n
print "The charge carries in zinc are positive."
```

In [3]:

```
import math
#Variable declaration
e = 1.602e-019; # Energy equivalent of 1 eV, J
k = 1.38e-023; # Boltzmann constant, J/K
T = 293; # Room temperature, K
V_f = 0.200; # Forward voltage, V
I_f = 50e-003; # Forward current, A
V_r = -0.200; # Reverse voltage, V
#Calculations
I_r = I_f*(math.exp(e*V_r/(k*T))-1)/(math.exp(e*V_f/(k*T)) - 1); # Reverse current from diode equation, A
#Result
print "The reverse current through pn-junction diode = %2d micro-ampere"%(I_r/1e-006)
```

In [4]:

```
import math
#Variable declaration
A = 100*100; # Area of solar cell, Sq.m
t = 12*60*60; # Time for which the solar cell operates, s
phi = 680; # Solar flux received by the solar cell, W/Sq.m
eta = 0.30 # Efficiency of the solar array
#Calculations&Results
E_array = eta*phi*A*t; # Energy produced by solar cell in one 12-hour day, J
print "The energy produced by solar cell in one 12-hour day : %3.1e J"%E_array
P = 100e+006; # Power output of power plant, W
t = 24*60*60; # Time for which power plant operates, s
E_plant = P*t; # Energy produced by power plant, J
print "The energy produced by power plant in one day : %3.1e J which is about %d times more than that produced by solar cell array..!"%(E_plant, math.ceil(E_plant/E_array))
```

In [5]:

```
import math
#Variable declaration
r1 = 2.30e-002; # Radius of inner edge of storing region of CD-ROM, m
r2 =5.80e-002; # Radius of outer edge of storing region of CD-ROM, m
A = math.pi*(r2**2 - r1**2); # Area of the usable region of CD-ROM, Sq.m
N = 700e+006*8; # Total number of bits in CD-ROM
#Calculations
APB = A/N; # Area per bit of CD-ROM, Sq.m/bit
t = 1.6e-006; # Track width of CD_ROM, m
l = APB/t; # Bit length, m
#Results
print "The surface area of CD-ROM allowed for each data bit = %3.1e Sq.m/bit"%APB
print "The approx. dimensions of each bit along the track = %1.0f micro-metre"%(l/1e-006)
```