Chapter 3: Resistance variation

Example 1, page no. 24

In [1]:
from __future__ import division
#initializing the variables:
R = 600; # in ohms
L = 5; # in meter
L1 = 8; # in meter
R2 = 420; # in ohms

#calculation:
R1 = R*L1/L
L2 = R2*L/R

#results
print "a)Resistance", R1,"Ohms"
print "b)Length:", L2,"meters(m)"

a)Resistance 960.0 Ohms
b)Length: 3.5 meters(m)

Example 2, page no. 24

In [3]:
from __future__ import division
#initializing the variables:
R = 300; # in ohms
A = 2; # in mm2
A1 = 5; # in mm2
R2 = 750; # in ohms

#calculation:
R1 = R*A/A1
A2 = R*A/R2

#results
print "(a)Resistance", R1,"Ohms"
print "(b)C.S.A:", A2,"mm^2"

(a)Resistance 120.0 Ohms
(b)C.S.A: 0.8 mm^2

Example 3, page no. 25

In [4]:
from __future__ import division
#initializing the variables:
R = 0.16; # in ohms
A = 3; # in mm2
L = 8; # in m
A1 = 1; # in mm2

#calculation:
L1 = L*3
R1 = R*A*L1/(A1*L)

#results
print "Resistance", R1,"Ohms"

Resistance 1.44 Ohms

Example 4, page no. 25

In [5]:
from __future__ import division
#initializing the variables:
A = 100E-6; # in m2
L = 2000; # in m
p = 0.03E-6; # in ohm m

#calculation:
R = p*L/A

#results
print "Resistance", R,"Ohms"

Resistance 0.6 Ohms

Example 5, page no. 25

In [1]:
from __future__ import division
#initializing the variables:
R = 0.25; # in ohms
L = 40; # in m
p = 0.02E-6; # in ohm m

#calculation:
A = p*L*1E6/R

#results
print "C.S.A ", A,"mm^2"

C.S.A  3.2 mm^2

Example 6, page no. 25

In [18]:
from __future__ import division
#initializing the variables:
R = 150; # in ohms
L = 1500; # in m
A = 0.17E-6; # in m2

#calculation:
p = R*A*1E6/L

#results
print "resistivity", p,"uOhm.m"

resistivity 0.017 uOhm.m

Example 7, page no. 26

In [1]:
from __future__ import division
import math
#initializing the variables:
d = 0.012; # in m
L = 1200; # in m
p = 1.7E-8; # in ohm m

#calculation:
A = math.pi*d*d/4
R = p*L/A

#results
print "resistance", round(R,3),"Ohm"

resistance 0.18 Ohm

Example 8, page no. 27

In [2]:
from __future__ import division
#initializing the variables:
R0 = 100; # in ohms
T0 = 0; # in °C
T1 = 70; # in °C
a0 = 0.0043; # in per°C

#calculation:
R70 = R0*(1 + (a0*T1))

#results
print "Resistance", R70,"Ohm"

Resistance 130.1 Ohm

Example 9, page no. 27

In [3]:
from __future__ import division
#initializing the variables:
R1 = 27; # in ohms
T0 = 0; # in °C
T1 = 35; # in °C
a0 = 0.0038; # in per°C

#calculation:
R0 = R1/(1 + (a0*T1))

#results
print "resistance", round(R0,2),"Ohm"

resistance 23.83 Ohm

Example 10, page no. 27

In [4]:
from __future__ import division
#initializing the variables:
R0 = 1000; # in ohms
T0 = 0; # in °C
T1 = 80; # in °C
a0 = -0.0005; # in per°C

#calculation:
R80 = R0*(1 + (a0*T1))

#results
print "resistance", R80,"Ohm"

resistance 960.0 Ohm

Example 11, page no. 28

In [5]:
from __future__ import division
#initializing the variables:
R20 = 10; # in ohms
T0 = 20; # in °C
T1 = 100; # in °C
a20 = 0.004; # in per°C


#calculation:
R100 = R20*(1 + (a20)*(T1 - T0))

#results
print "resistance", R100,"Ohm"

resistance 13.2 Ohm

Example 12, page no. 28

In [6]:
from __future__ import division
#initializing the variables:
R18 = 200; # in ohms
R1 = 240; # in ohms
T0 = 18; # in °C
a18 = 0.0039; # in per°C


#calculation:
T1 = (((R1/R18)-1)/a18) + T0

#results
print "Temperature", round(T1,2),"degC"

Temperature 69.28 degC

Example 13, page no. 29

In [7]:
from __future__ import division
#initializing the variables:
R20 = 200; # in ohms
T0 = 20; # in °C
T1 = 90; # in °C
a0 = 0.004; # in per°C


#calculation:
R90 = R20*(1 + (a0*T1))/(1 + (a0*T0))

#results
print "Resistance", round(R90,0),"ohms"

Resistance 252.0 ohms