Download Basic Electrical Engineering C L Wadhwa Pdf

Hello Engineers if you are looking for the free download link of Basic Electrical Engineering C L Wadhwa pdf then you each the right place. Today team Electrical Learners share with you C L Wadhwa Basic Electrical Engineering Pdf. This book will help you in Your academic examination or competitive examinations. You can download this book just simply click on Download Pdf 

Contents:

• D.C. Circuits
• Electromagnetic Induction 
• A.C. Circuits 
• Network Theory 
• Three Phase Supply 
• Basic Instruments 
• Transformer 
• D.C. Machines 
• Three-Phase Synchronous Machines 
• Three-Phase Induction Motors 
• Single Phase Induction Motors 
• Power System 
• Domestic Wiring
• Multiple Choice Questions
• Reference
• Index

Download PDF

It's more important to know about the Faraday's laws of electromagnetic Induction .

Faraday's laws of electromagnetic Induction :

We have two laws mainly

First Law :

It states : Whenever the magnetic flux linked with a circuit changes, an e.m.f. is always induced in it.

or

 Whenever a conductor cuts magnetic flux, an e.m.f. is induced in that conductor.

Second Law :

It states : The magnitude of the induced e.m.f. is equal to the rate of change of flux-linkages.

Induced EMF e = -NdΦ/DT

Please Comment Below If You Have Any Suggestions Or Doubts Regarding This Topic

Production of Induced EMF And Current

Production of Induced EMF And Current


In Fig.  is shown an insulated coil whose terminals are connected to a sensitive galvanometer
G. It is placed close to a stationary bar magnet initially at position AB (shown dotted). As seen, some
flux from the N-pole of the magnet is linked with or threads through the coil but, as yet, there is no
deflection of the galvanometer. Now, suppose that the magnet is suddenly brought closer to the coil in
position CD (see figure). Then, it is found that there is a jerk or a sudden but a momentary deflection
in the galvanometer and that this lasts so long as the magnet is in motion relative to the coil, not
otherwise. The deflection is reduced to zero when the magnet becomes again stationary at its new
position CD. It should be noted that due to the approach of the magnet, flux linked with the coil is
increased.

Next, the magnet is suddenly withdrawn away from the coil as in Fig. 7.2. It is found that again
there is a momentary deflection in the galvanometer and it persists so long as the magnet is in
motion, not when it becomes stationary. It is important to note that this deflection is in a direction
opposite to that of Fig. 7.1. Obviously, due to the withdrawal of the magnet, flux linked with the coil
is decreased.

The deflection of the galvanometer indicates the production of e.m.f. in the coil. The only cause
of the production can be the sudden approach or withdrawal of the magnet from the coil. It is found
that the actual cause of this e.m.f. is the change of flux linking with the coil. This e.m.f. exists so long
as the change in flux exists. Stationary flux, however strong, will never induce any e.m.f. in a station￾ary conductor. In fact, the same results can be obtained by keeping the bar magnet stationary and
moving the coil suddenly away or towards the magnet.

Relation Between Magnetism And Electricity

Hey I am Here to discuss about the Small Topic  Relation between Magnitism And Electricity

Relation Between Magnetism And Electricity

It is well known that whenever an electric current flows through a conductor, a magnetic field is

immediately brought into existence in the space surrounding the conductor. It can be said that when

electrons are in motion, they produce a magnetic field. The converse of this is also true i.e. when a

magnetic field embracing a conductor moves relative to the conductor, it produces a flow of electrons

in the conductor. This phenomenon whereby an e.m.f. and hence current (i.e. flow of electrons) is

induced in any conductor which is cut across or is cut by a magnetic flux is known as electromagnetic

induction. 

The historical background of this phenomenon is this :

After the discovery (by Oersted) that electric current produces a magnetic field, scientists began

to search for the converse phenomenon from about 1821 onwards. The problem they put to them￾selves was how to ‘convert’ magnetism into electricity. It is recorded that Michael Faraday* was in

the habit of walking about with magnets in his pockets so as to constantly remind him of the problem.

After nine years of continuous research and experimentation, he succeeded in producing electricity

by ‘converting magnetism’. In 1831, he formulated basic laws underlying the phenomenon of elec￾tromagnetic induction (known after his name), upon which is based the operation of most of the

commercial apparatus like motors, generators and transformers etc.

Force on a Current-carrying Conductor Lying in a Magnetic Field & Fleming left hand rule

Hello I am Here to present an important topic and most exciting topic

Electromagnetism

Force on a Current-carrying Conductor Lying in a Magnetic Field

It is found that whenever a current-carrying conductor is placed in magnetic field, it experiences a

 force which acts in a direction perpendicular both to the direction of the current and the field. In Fig

. is shown a conductor XY lying at right angles to the uniform horizontal field of flux density B Wb

/m2

 produced by two solenoids A and B. If l is the length of the conductor lying within this field and

 I ampere  the

current carried by it, then the magnitude of the force experienced by it is

the BIl = µ0 µr HIl newton

Using vector notation

F

= I l B

F = IlB sin θ where θ is the angle between l

which

is 90º in the present case

or F = Il B sin 90º = Il B newtons (∵ sin 90º = 1)

The direction of this force may be easily found by Fleming’s left-hand rule.

Hold out your left hand with forefinger, second finger and thumb at right angles to one another.
If the forefinger represents the direction of the field and

the second finger that of the current, then thumb gives the direction

 of the motion. It is illustrated in Fig.

shows another method of finding the direction of force acting on a current carrying conductor. It is
known as Flat Left Hand rule. The force acts in the direction of the thumb obviously, the direction of motor of the

conductor is the same as that of the force. It

 should be noted that no force is exerted on a con￾ductor when it lies parallel to the magnetic field. In general, if the conductor lies at an angle θ with the direction

of the field, then B can be resolved into two components,
B cos θ parallel to and B sin θ perpendicular to the con￾ductor. The former produces no effect whereas the latter is
responsible for the motion observed. In that case,

Fleming left hand rule

F = BIl sin θ newton, which has been expressed as
cross product of vector above.

Absolute & Relative Permiability & Flux Density

Absolute Permeability (μ) and Relative Permeability (μr) 

Magnetic lines

 a bar of a magnetic material, say, iron placed in a uniform field of strength H N/Wb. Suppose, a flux density of B Wb/m2

 is developed in the rod.

Then, the absolute permeability of the material of the rod is defined as
μ = B/H henry/metre 
or 
B = μH 
    = µ0 µr H Wb/m2 ...(i)
When H is established in air (or vacuum), then corresponding flux density developed in air is

B0 = µ0 H

Now, when iron rod is placed in the field, it gets magnetised by induction. If induced pole strength in the rod is m Wb, then a flux of m Wb emanates from its N-pole, re-enters its S-pole and continues from S to N-pole within the magnet. If A is the face or pole area of the magentised iron bar, the induction flux density in the rod is


Bi = m/A Wb/m2

Hence, total flux density in the iron rod consists of two parts 

(i) B0 –flux density in air even when rod is not present
(ii) Bi–induction flux density in the rod


B = B0 + Bi
 = µ0 H + m/A


Eq. (i) above may be written as 
B = µr . µ0 H 
    = µr B0

µr =B/B0

Hence, relative permeability of a material is equal to the ratio of the flux density produced in that material to the flux density produced in vacuum by the same magnetising force.

Flux Density (B) 

 It is given by the flux passing per unit area through a plane at right angles to the flux. It is usually designated by the capital letter B and is measured in weber/meter2 . It is a Vector Quantity. It ΦWb is the total magnetic flux passing normally through an area of A m^ 2
, then
B = Φ/A      Wb/m^2  or tesla (T)

Intensity of Magnetisation (I)

It may be defined as the induced pole strength developed per unit area of the bar. Also, it is the magnetic moment developed per unit volume of the bar.

Let


 m = pole strength induced in the bar in Wb
A = face or pole area of the bar in m^2

Then
 I = m/A    Wb/m^2
Hence, it is seen that intensity of magnetisation of a substance may be defined as the flux density
produced in it due to its own induced magnetism.

If l is the magnetic length of the bar, then the product (m × l) is known as its magnetic moment M.

I= m/A
  = m×l / A×l
  = m/V
  = Magnetic Moment / Volume

Laws of Magnetic Force & Magnetic Field Strength & Magnetic Potential

Here we are going to discuss about magnitism

Magnet

Laws of magnetic Force :

Coulomb was the first to determine experimentally the quantitative expression for the magnetic force between two isolated point poles. It may be noted here that, in view of the fact that magnetic poles always exist in pairs, it is impossible, in practice, to get an isolated pole. The concept of an isolated pole is purely theoretical. However, poles of a thin but long magnet may be assumed to be point poles for all practical purposes  By using a torsion balance, he found that the force between two magnetic poles placed in a medium is


(i) directly proportional to their pole strengths

(ii) inversely proportional to the square of the distance between them and


(iii) inversely proportional to the absolute permeability of the surrounding medium.

Magnetic Field Strength (H)

Magnetic lines

Magnetic lines of force

Magnetic field strength at any point within a magnetic field is numerically equally to the force experienced by a N-pole of one weber placed at that point. Hence, unit of H is N/Wb. Suppose, it is required to find the field intensity at a point A distant r metres from a pole of m webers. Imagine a similar pole of one weber placed at point A. The force experienced by this pole is

Magnetic Potential :

The magnetic potential at any point within a mag￾netic field is measured by the work done in shifting a N-pole of one weber from infinity to that point against the force of the magnetic field. It is given by

Charging and Discharging of Capacitor

It's time to Know about Charging and Discharging of Capacitor

Capacitor

Charging Of A Capacitor :

Consider a series RC network connected to a battery of voltage 'V' through a switch 'S' . Let us assume that the Capacitor initially uncharged. There is no current when switch'S' is opened.

If the Switch is closed at t=0 there will be a current through resistor and Capacitor will begin to charge . Note that during charging process the charge transfered from one place to other through the resistor , switch and battery untill the Capacitor is fully charged . The maximum Charge depends upon the EMF the battery . Once the maximum charge is reached the current in the circuit is zero. Suppose at any instant during charging the circuit current is 'I' and Charge on the Capacitor is 'q' 

Applying Kirchoff's Voltage law 

V-IR-q/C = 0

RC series Circuit

Initial Current :

At t=0 when the Switch is closed , the charge on the Capacitor is zero therefore the current is maximum (I0) and is given by

I0 = V/R -------------------at t=0

Charge on the Capacitor at any instant during charging :

The charge 'q' at any time during charging can be shown to be 

q = Q(1-e^[-t/RC])
                             Q= Max Charge on capacitor = CV
Time constant  て = RC

q= Q(1-[e^(-t/て)])

Charging of capacitor

Voltage across capacitor at any instant during charging :

It can be shown mathematically that Voltage 'v' across capacitor at any time during charging is given by

v =  V(1-e^[-t/て])
V = final Voltage

Discharging of a Capacitor :

Consider the circuit I) consisting of a capacitor with an initial Charge "Q" , a resistor R and a switch "S" when the Switch is open. There is a potential difference  of Q/C across the Capacitor and zero potential difference across the resistor since I=0

Discharging of Capacitor

If the Switch is closed at t=0 the Capacitor begins to discharge through the resistor . At the same time during Discharging . Let Circuit current be I and Charge on capacitor  "q" . According to Kirchoff's Voltage Law potential drop across resistor = (IR) must be equal to potential difference across the Capacitor = (q/C)

IR = q/C

However the current in the circuit must be equal to the rate of decrease of charge on the Capacitor 

I.e  I = -dq/DT

Therefore 

This we see that both the charge on the Capacitor and the circuit current delay exponentially at a rate determined by the time constant て=RC

Discharging of Capacitor

Energy stored in the Capacitor & Energy Density

I am here now to discuss about the Energy stored in Capacitor

Capacitor

Energy Stored In a Capacitor :

Consider a parallel plate Capacitor it initially uncharged so that the initial potential difference across the plates is zero

Now imagine that the Capacitor is connected to a battery which develops a maximum charge "q" and a final potential across the plates is "V" 
Since the Capacitor is charged linearly the q-V graph is straight line passing through the origin

q-V Characteristics

Since the initial potential difference is zero, the average potential difference during the charging process

= (0+V)
= V/2

Energy Stored  U = V/2 ×q = 1/2 qV


The energy stored in the Capacitor can be expressed in alternate forms

•It is clear from the above expression that energy stored increases with increase of potential difference.



Energy Density :


The energy stored in the Capacitor can be considered as being stored in the Electric field created between the plates as the Capacitor is charged 

Consider a parallel plate Capacitor with  Area of Plate "A" and separation "d" 

Parallel plate Capacitor

Energy stored 
U = 1/2 CV^2

The energy stored per unit volume is called energy Density (u) since the volume of parallel plate is 'Ad'

Therefore energy Density ( i.e Electric field energy stored per unit volume ) in any region of space is directly proportional to the square of the Electric field Intensity in the region

Related Links :

Capacitor & Capacitance
Capacitance of parallel plate Capacitor