Chapter 11: Measurement of Voltages and Currents

Example 11.1, Page 209

In [2]:
#Initialisation
t=0.02                   #time period in seconds from diagram
v1=7                     #peak voltage from diagram


#Calculation
f=1*t**-1               #frequency in Hz
v2=2*v1                 # Peak to Peak Voltage

#Result
print'Frequency = %d Hz\n'%f
print'Peak to Peak Voltage = %d V\n'%v2

Frequency = 50 Hz

Peak to Peak Voltage = 14 V

Example 11.2, Page 210

In [26]:
import math
#Initialisation
t=0.05                   #time period in seconds from diagram
v1=10                     #peak voltage from diagram


#Calculation
f1=1*t**-1               #frequency in Hz
w1=2*math.pi*f1          #Angular velocity

#Result
print'%d sin %.1ft Hz\n'%(v1,w1)

10 sin 125.7t Hz

Example 11.3, Page 211

In [24]:
import math
#Initialisation
t=0.1                   #time period in seconds from diagram
v1=10                     #peak voltage from diagram
t1=25*10**-3

#Calculation
f1=1*t**-1               #frequency in Hz
w1=2*math.pi*f1          #Angular velocity
phi=-(t1*t**-1)*360      #phase angle

#Result
print'phi = %d degree'%phi
print'%d sin %dt%d Hz\n'%(v1,round(w1),phi)

phi = -90 degree
10 sin 63t-90 Hz

Example 11.4, Page 215

In [27]:
import math
#Initialisation
v1=5                                 #constant 5V
r=10                                #resistance in Ohm
vrms=5                              #sine wave of 5 V r.m.s
vp=5                                #5 V peak

#Calculation
p=(v1**2)*r**-1                      #Power in watts
p2=(vrms**2)*r**-1                   #Power avarage in watts
a=(vp*math.sqrt(2)**-1)**2
p3=a*r**-1                           #Power avarage in watts                         

#Result
print'(1) P = %.1f W\n'%p
print'(2) Pav = %.1f W\n'%p2
print'(3) Pav = %.2f W\n'%p3

(1) P = 2.5 W

(2) Pav = 2.5 W

(3) Pav = 1.25 W

Example 11.5, Page 220

In [10]:
#Initialisation
fsd1=50*10**-3                #full scale defelction of ammeter in Ampere
fsd2=1*10**-3                 #full scale defelction of moving coil meter in Ampere
Rm=25                         #resistance of moving coil meter in Ohms

#Calculation
Rsm=fsd1*fsd2**-1             #sensitivity factor
Rsh=Rm*49**-1                 #shunt resistor

#Result
print'Therefore, Resistor = %d mOhm\n'%round(Rsh*10**3)

Therefore, Resistor = 510 mOhm

Example 11.6, Page 222

In [5]:
#Initialisation
fsd1=50                       #full scale defelction of voltmeter in Volts
fsd2=1*10**-3                 #full scale defelction of moving coil meter in Ampere
Rm=25                         #resistance of moving coil meter in Ohms

#Calculation
Rsm=fsd1*fsd2**-1
Rse=Rsm-Rm

#Result
print'Rse = %.3f KOhm\n'%(Rse*10**-3)
print'Therefore, Resistor ~ %d KOhm\n'%round(Rse*10**-3)

Rse = 49.975 KOhm

Therefore, Resistor ~ 50 KOhm
In [ ]: