# Chapter4 - Measurement of Resistance¶

## Exa 4.1 page 121¶

In [2]:
from __future__ import division
from math import log10
t=20
C=8*10**-10
E=200
e=150
a=log10(E/e)
R=(0.4343*t)/(C*a)*10**-6
print "Insulation resistance = %.2f mega-ohm"%(R)

Insulation resistance = 86902.59 mega-ohm


## Exa 4.2 page 121¶

In [10]:
t=600
C=2.5*10**-12
E=500
e=300
a=log10(E/e)
R=(0.4343*t)/(C*a)
print "Insulation resistance=%.2f mega-ohm"%(R/1e6)

Insulation resistance=469833614.93 mega-ohm


## Exa 4.3 page 122¶

In [4]:
from math import log
#V=Eexp(-t/tc)   where tc= RC=Time constant
t=30
V=125
E=200
tc=-30/log(V/E)
R=(7/15)*tc-7
print "Insulation resistance=%.2f mega-ohm"%(R)

Insulation resistance=22.79 mega-ohm


## Exa 4.4 page 122¶

In [5]:
Q=3000
S=0.1
M=2000
X=Q*S/M
print "The value of X=%.2f ohm"%(X)

The value of X=0.15 ohm


## Exa 4.5 page 122¶

In [6]:
lx=55
ly=100-lx
Y=100
X=Y*(lx/ly)
print "Resistance of the field coil=%.2f ohm"%(X)

Resistance of the field coil=122.22 ohm


## Exa 4.6 page 122¶

In [7]:
p=200.7
q=400
S=200.05*10**-6
P=200.5
Q=400
r=1400*10**-6
X=((P*S/Q)+((q*r)/(p+q))*((P/Q)-(p/q)))*10**6
print "Unknown resistance=%.2f micro-ohm"%(X)

Unknown resistance=99.81 micro-ohm


## Exa 4.7 page 123¶

In [8]:
E=230
V1=60
V2=40
Rv=50000
R1=((E-(V1+V2))/V2)*Rv*10**-3
print "Resistance between positive and earth=%.2f Kohm"%(R1)
R2=((E-(V1+V2))/V1)*Rv*10**-3
print "\nResistance between -ve and earth=%.2f Kohm"%(R2)

Resistance between positive and earth=162.50 Kohm

Resistance between -ve and earth=108.33 Kohm


## Exa 4.8 page 124¶

In [9]:
Q=100.5
M=300
q=100.6
m=300.25
r=0.1
S=0.0045
X=((M*S/Q)+((r)/(r+m*q))*((M*q/Q)-(m)))*10**6
print "Unknown resistance=%.2f micro-ohm"%(X)

Unknown resistance=13433.00 micro-ohm