In [1]:

```
import math
#Variables
PZM = 500 #Power rating of zener diode (in milli-watt)
VZ = 6.8 #Zener voltage rating (in volts)
#Calculation
IZM = PZM / VZ #Maximum value of zener current (in milli-Ampere)
#Result
print "THe value of IZM for the device is ",round(IZM,1)," mA."
```

In [2]:

```
import math
#Variables
PZM = 500 #Power rating of zener diode (in milli-watt)
df = 3.33 #derating factor (in milli-watt)
T1 = 75 #Temperature (in degree Celsius)
T2 = 50 #Temperature (in degree Celsius)
#Calculation
Tdf = df * (T1 - T2) #Total derating factor (in milli-watt)
PZ = PZM - Tdf #Maximimum power dissipating for the device (in milli-watt)
#Result
print "The maximum power dissipation for the device is ",PZ," mW."
```

In [3]:

```
import math
#Variables
IZ1 = 20 #Reverse current (in milli-Ampere)
IZ2 = 30 #Reverse current (in milli-Ampere)
VZ1 = 5.6 #Zener voltage (in volts)
VZ2 = 5.65 #Zener voltage (in volts)
#Calculation
dIZ = IZ2 - IZ1 #Change in reverse current (in milli-Ampere)
dVZ = VZ2 - VZ1 #Change in zener voltage (in volts)
rZ = dVZ / (dIZ * 10**-3) #Resistance of device (in ohm)
#Result
print "Resistance of the zener diode is ",rZ," ohm."
```

In [4]:

```
import math
#Variables
VZ = 4.7 #Zener voltage (in volts)
rZ = 15 #Resistance (in ohm)
IZ = 20 * 10**-3 #Current (in Ampere)
#Calculation
VZ1 = VZ + IZ * rZ #Terminal voltage of a zener diode (in volts)
#Result
print "Terminal voltage of the zener diode is ",VZ1," V."
```

In [1]:

```
import math
#Variables
C1min = C2min = Cmin = 5 #Minimum capacitance (in pico-farad)
C1max = C2max = Cmax = 50 #Maximum capacitance (in pico-farad)
L = 10 #Inductance (in milli-Henry)
#Calculation
CTmin = C1min * C2min / (C1min + C2min) #Total minimum capacitance (in pico-farad)
CTmin = CTmin * 10**-12 #Total minimum capacitance (in farad)
L = 10 * 10**-3 #Inductance (in Henry)
f0max = 1/(2*math.pi*(L*CTmin)**0.5) #Maximun resonant frequency (in Hertz)
CTmax = C1max * C2max / (C1max + C2max) #Total maximum capacitance (in pico-farad)
CTmax = CTmax * 10**-12 #Total minimum capacitance (in farad)
f0min = 1/(2*math.pi*(L*CTmax)**0.5) #Minimum resonant frequency (in Hertz)
#Result
print "Tuning range for the circuit is between ",round(f0min * 10**-3)," kHz and ",round(f0max * 10**-6,0)," MHz."
```

In [6]:

```
import math
#Variables
T = 0.04 * 10**-6 #Time period (in seconds)
#Calculation
f = 1/T #Frequency (in Hertz)
f = f * 10**-6 #Frequency (in Mega-Hertz)
f5 = 5 * f #%th - harmonic (in Mega-Hertz)
#Result
print "Frequency of 5th harmonic is ",f5," MHz."
```

In [7]:

```
import math
#Variables
Vout = 8.0 #Output voltage (in volts)
VFmin = 1.8 #LED min voltage (in volts)
VFmax = 2.0 #LED max voltage (in volts)
IFmax = 16 * 10**-3 #Maximum current (in Ampere)
#Calculation
RS = (Vout - VFmin) / IFmax #Current limiting Resistor (in ohm)
RS1 = (Vout - VFmax) / IFmax #Current limiting Resistor 1 (in ohm)
#Result
print "In either case , the smallest standard-value resistor that has a value greater than ",RS, " ohm or ",RS1," ohm is the 390 ohm resistor.\nTherefore Rs should be 390 ohm."
```

In [8]:

```
import math
#Variables
VDmin = 1.5 #minimum voltage drop (in volts)
VDmax = 2.3 #maximum voltage drop (in volts)
VS = 10 #Source voltage (in volts)
R1 = 470 #Resistance (in ohm)
#Calculation
Imax = (VS - VDmin) / R1 #Maximum current (in Ampere)
Imin = (VS - VDmax) / R1 #Minimum current (in Ampere)
#Result
print "Minimum value of LED current is ",round(Imin * 10**3,1)," mA.\nMaximum value of LED current is ",round(Imax * 10**3,1)," mA."
```

In [9]:

```
import math
#Variables
VDmin = 1.8 #minimum voltage drop (in volts)
VDmax = 3.0 #maximum voltage drop (in volts)
#Calculation
#Case 1
VS = 24.0 #Source voltage (in volts)
RS = 820.0 #Resistance (in ohm)
Imax = (VS - VDmin) / RS #Maximum current (in Ampere)
Imin = (VS - VDmax) / RS #Minimum current (in Ampere)
dI = Imax - Imin #Change in current (in Ampere)
#Case 2
VS1 = 5.0 #Source voltage (in volts)
RS1 = 120.0 #Resistance (in ohm)
Imax1 = (VS1 - VDmin) / RS1 #Maximum current (in Ampere)
Imin1 = (VS1 - VDmax) / RS1 #Minimum current (in Ampere)
dI1= Imax1 - Imin1 #Change in current (in Ampere)
#Result
print "Since change in current in case 1 i.e",round(dI*10**3,2),"mA is less than change in current in case 2 i,e,",round(dI1* 10**3,2)," mA."
print "Therefore brightness in the first case will remain constant."
#printing mistake in book for value of VDmin. It should be 1.8 volts instead of 1.1 volts.
```

In [10]:

```
import math
#Variables
R1 = 100.0 * 10**3 #Resistance when illuminated (in ohm)
r = 1.0 * 10**3 #cell resistance (in ohm)
I = 10.0 * 10**-3 #Current (in Ampere)
VS = 30 #Source voltage (in volts)
#Calculation
R = VS/I - r #R is the series resitance (in ohm)
Id = VS / (R + R1) #Dark current (in Ampere)
#Result
print "Ther series resistance required is ",R/1000," kilo-ohm.\nThe dark current is ",round(Id * 10**3,1)," A."
```

In [11]:

```
import math
#Variables
V = 12.0 #Battery voltage (in volts)
I = 0.5 #Current (in Ampere)
T = 24 #Time period (in hours)
V1 = 0.5 #Voltage by each cell (in volts)
I1 = 50 * 10**-3 #Current in each cell (in Ampere)
#Calculation
VS = 13.5 #Solar bank voltage (in volts)
n = VS / V1 #Number of series connected solar cells
Q = T/2 * I #Charge given out in one day (in Ampere-Hour)
I2 = Q / (T/2) #Charging current (in Ampere)
N = I2/I1 #Number of groups of solar cell required
nT = n * N #Total number of solar cells required
#Result
print "Total cells required is ",nT,"."
```