# Chapter 20: Alternating Currents and Electronics¶

## Ex20.1:pg-982¶

In [4]:
  #Example 20_1
import math
#To findout the time that it has to wait after turning off the set before it is safe to touch capacitor
r=10.0**6          #Units in Ohms
c=10.0**-5             #Units in F
ti=r*c           #Units in Sec
print "We have to wait for a time of t=",round(ti)," sec"

We have to wait for a time of t= 10.0  sec


## Ex20.2:pg-983¶

In [2]:
  #Example 20_2

import math

#To find the rms current in the circuit
f=20         #Units in Hz
c=4*10.0**-7         #Units in F
xc=1/(2.0*math.pi*f*c)           #Units in Ohms/sec
f=2*10**6          #Units in Hz
xc1=1/(2*math.pi*f*c)           #Units in Ohms/sec
v=80.0           #Units in V
i=v/xc            #Units in A
i1=v/xc1            #Units in A
print "The RMS current when f=20 Hz is=",round(i,5)," Ohms\nThe RMS current when f=2*10**6 Hz is=",round(i1,2)," Ohms"

The RMS current when f=20 Hz is= 0.00402  Ohms
The RMS current when f=2*10**6 Hz is= 402.12  Ohms


## Ex20.3:pg-984¶

In [5]:
  #Example 20_3
import math

#To find the current through the inductor
f=60             #Units in Hz
l=15.0*10**-3           #Units in H
xl=2*math.pi*f*l           #Units in Ohms
v=40          #Units in V
i=v/xl           #Units in A
print "The current in the inductor when frequency=60 Hz is I=",round(i,2)," A"
f=6.0*10**5             #Units in Hz
l=15.0*10**-3           #Units in H
xl=2*math.pi*f*l           #Units in Ohms
v=40          #Units in V
i=v/xl           #Units in A
print "\nThe current in the inductor when frequency=6*10**2 Hz is I=",round(i,6)," A"

The current in the inductor when frequency=60 Hz is I= 7.07  A

The current in the inductor when frequency=6*10**2 Hz is I= 0.000707  A


## Ex20.4:pg-984¶

In [2]:
  #Example 20_4
import math

#To find current in circuit, Voltmeter reading, reading across capacitor and power loss
f=2000             #Units in Hz
c=0.6*10**-6           #Units in F
xc=1/(2*math.pi*f*c)           #Units in Ohms
r=300          #Units in Ohms
z=math.sqrt(r**2+xc**2)        #Units in Ohms
v=80          #Units in V
i=v/z            #Units in A
vr=i*r      #Units in V
vc=i*xc          #Units in V
p=i**2*r           #Units in W
print "The current in circuit is I=",round(i,4)," A\nVolt meter readings across resistor Vr=",round(vr,1)," V\nReadings across capacitor is Vc=",round(vc,1)," V\nPower loss in circuit is=",round(p,1)," W"

The current in circuit is I= 0.2439  A
Volt meter readings across resistor Vr= 73.2  V
Readings across capacitor is Vc= 32.3  V
Power loss in circuit is= 17.8  W


## Ex20.5:pg-984¶

In [3]:
  #Example 20_5

import math
#To find the current in circuit and voltmeters reading across R C and L
f=600           #Units in Hz
l=4.0*10**-3           #Units in H
xl=2*math.pi*f*l          #Units in Ohms
c=10.0*10**-6           #Units in F
xc=1/(2*math.pi*f*c)         #Units in Ohms
r=20.0         #Units in Ohms
z=math.sqrt(r**2+(xl-xc)**2)        #Units in Ohms
v=50.0           #Units in V
i=v/z          #Units in A
vr=i*r      #Units in V
vl=i*xl        #Units in V
vc=i*xc      #Units in V
print "The current in circuit is I=",round(i,2)," A\nVolt meter reading across R Vr=",round(vr,1)," V\nVolt meter reading across L Vl=",round(vl,1)," V\nVolt meter reading across c Vc=",round(vc,1)," V\n"

The current in circuit is I= 2.17  A
Volt meter reading across R Vr= 43.4  V
Volt meter reading across L Vl= 32.7  V
Volt meter reading across c Vc= 57.6  V