# Chapter 20 : Induced voltages and inductance¶

## Example 20.1 Page No: 665¶

In [4]:
B=.5 # in T
A=3.24*10**-4 # in m**2
Flux=B*A
N=25
delta_t=.8
print "Magnetic flux = %0.2e T.m**2"%Flux
e=(N*Flux)/(delta_t)
print "Induced emf = %0.2e volt"%e

Magnetic flux = 1.62e-04 T.m**2
Induced emf = 5.06e-03 volt


## Example 20.2 Page No: 667¶

In [6]:
B=.6*10**-4 # in T
l=30
v=250 # in m/s
e=B*l*v
print "Induced emf = %0.2f volt"%e

Induced emf = 0.45 volt


## Example 20.3 Page No: 672¶

In [7]:
B=.25 # in T
l=.5
v=2 # in m/s
e=B*l*v
print "Solution a"
print "Induced emf = %0.2f volt"%e
R=.5 # in ohm
I=e/R

print "Solution b"
print "Current = %0.2f A"%I
delta_v=.25
P=I*delta_v
print "Solution c"
print "Power = %0.2f watt"%P
t=1 # in s
w=P*t
print "Energy delivered = %0.2f J"%w
#  Answer give for J in textbook is wrong
d=v*t
F=w/d
print "Solution d"
print "Force = %0.2f N"%F

Solution a
Induced emf = 0.25 volt
Solution b
Current = 0.50 A
Solution c
Power = 0.12 watt
Energy delivered = 0.12 J
Solution d
Force = 0.06 N


## Example 20.5 Page No: 678¶

In [9]:
from math import pi
f=60 # in Hz
w=2*pi*f
N=8
A=.09 # in m**2
B=.5 # in T
emf=N*A*B*w
print "Solution a"
print "Induced emf = %0.2f volt"%emf
R=12 # in ohm
I=emf/R
print "Solution b"
print "Current = %0.2f A"%I

print "Solution c"
print "Emf in Volt 136*sinwt"

Solution a
Induced emf = 135.72 volt
Solution b
Current = 11.31 A
Solution c
Emf in Volt 136*sinwt


## Example 20.6 Page No: 680¶

In [10]:
emf=120 # in Volt
R=10 # in Ohm
e_back=70
I=emf/R
print "Solution a"
print "Maximum Current = %0.2f A"%I
print "Solution b"
I=(emf-e_back)/R
print "Current = %0.2f A"%I

Solution a
Maximum Current = 12.00 A
Solution b
Current = 5.00 A


## Example 20.8 Page No: 684¶

In [12]:
from math import pi
uo=4*pi*10**-7 # in m/A
N=300
A=4*10**-4 # in m**2
l=25*10**-2
L=(uo*N*N*A)/l
print "Solution a"
print "Inductance = %0.2e H"%L
delta_I=-5
delta_t=1
e=(-L*delta_I)/(delta_t)
print "Solution b"
print "Emf = %0.2e Volt"%e

Solution a
Inductance = 1.81e-04 H
Solution b
Emf = 9.05e-04 Volt


## Example 20.9 Page No: 685¶

In [14]:
L=30*10**-3 # in Henry
R=6 # in Ohm
tou=L/R
print "Solution a"
print "Time constant = %0.2e s"%tou

e=12
I=(0.632*e)/R

print "Solution b"
print "Current = %0.2f Amps"%I

Solution a
Time constant = 5.00e-03 s
Solution b
Current = 1.26 Amps