Chapter 17 Transient Current

Example 17.1 Page no 534

In [7]:
#Given
E=3                           #V
L=2.5                        #H
R=50.0                       #ohm

#Calculation
T=L/R
L1=E/L
I0=E/R

#Result
print"(i) Time constant is", T,"S"
print"(ii) Rate of change of current is",L1,"A/S"
print"(iii) Maximum current is",I0,"A"

(i) Time constant is 0.05 S
(ii) Rate of change of current is 1.2 A/S
(iii) Maximum current is 0.06 A

Example 17.2 Page no 534

In [15]:
#Given
E=1                                  #V
R=1                                  #ohm
L=1                                  #H
t=1                                  #S
a=2.3036

#Calculation
import math
I=1-math.exp(-E/L)
t=a*math.log10(2)

#Result
print"(i) Current after 1 S is", round(I,3),"A"
print"(ii) Time to take the current to reach half its final value is",round(t,3),"S"

(i) Current after 1 S is 0.632 A
(ii) Time to take the current to reach half its final value is 0.693 S

Example 17.3 Page no 534

In [19]:
#Given
I0=2                         #A
L=0.1                          #H
R=20                           #ohm
I=0.3      
a=3.333
b=200.0

#Calculation
import math
t=2.3026*math.log10(a)/b
l=R*I*I0/L

#Result
print"Rate of change of current is", l,"A/s"

Rate of change of current is 120.0 A/s

Example 17.4 Page no 535

In [29]:
#Given
R=2*10**6                          #ohm
C=10**-6                           #farad
q=0.8647
a=0.1353

#Calculation
import math
t=-2*2.3026*math.log10(a)

#Result
print"Time is", round(t,0),"S"

Time is 4.0 S

Example 17.5 Page no 535

In [36]:
#Given
C=1.443*10**-6                    #F
t=60                             #S

#Calculation
import math
a=2.303*math.log10(2)
R=t/(C*a)

#Result
print"Value of resistance is", round(R*10**-6,0),"*10**6 ohm"

Value of resistance is 60.0 *10**6 ohm

Example 17.6 Page no 535

In [52]:
#Given
L=200*10**-6                       #H
f1=8*10**5
f2=12*10**-5                         #Hz

#Calculation
import math
C1=1/(4*math.pi**2*f1**2*L)
C=1/(4*math.pi**2*f2**2*L)

#Result
print"Range of capacitor C is",round(C*10**-8,0),"pF"
print"Range of capacitor C1 is",round(C1*10**12,0),"pF"

Range of capacitor C is 88.0 pF
Range of capacitor C1 is 198.0 pF