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ELECTRIC CIRCUIT ANALYSIS-PART A

PREPARED BY N.SHANKAR

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UNIT-I

1. DEFINE CURRENT?

Current is defined as the rate of flow of charge (free electrons).Current is

represented by I and its unit is Ampere.

2. DEFINE VOLTAGE?

Voltage is defined as the potential difference between ends of the conductor.

Voltage is represented by V and its unit is Volts.

3. STATE OHMS LAW?

It states that the voltage across the resistor is directly proportional to the current

flowing through the resistor.

4. DEFINE POWER?

Power is define as rate of doing work and its unit is Watt or Joule/sec.

(Or)

It is the product of current and voltage

5.

STATE KIRCHOFFS CURRENT LAW?

It states that algebraic sum of the currents meeting at any junction is zero.

(Or)

It can be also stated that sum of current entering the junction is equal to the sum

of current leaving the junction.

V=I*R

P=V*I

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6. STATE KIRCHOFFS VOLTAGE LAW?

It states that in a closed circuit the algebraic sum of product of the current and

resistance of all the elements plus the algebraic sum of the EMF induced in the circuit is

equal to zero.

(OR)

It can be stated that the sum of the voltage drops is equal to the sum of voltage

drop.

7. DEFINE ACTIVE ELEMENT?

Active element is defined as the energy sources. It can be either voltage or currentsources. Example: Transistor.

8. DEFINE PASSIVE ELEMENT?

Passive element is defined as the one which dissipates energy in form of heat or

which stores energy. Example: resistance, inductance.

9. DEFINE NETWORK?

Interconnections of circuit elements are called network.

10.DEFINE CIRCUITS?

ANetwork that contains at least one closed path is known as circuits.

IR+ EMF=0

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11.WHAT IS MEAN BE LUMPED PARAMETER NETWORK?

A network consisting of physically separated elements such as resistor, capacitor

is known as lumped parameter network.

Example: RLC network.

12.DEFINE DISTRIBUTED PARAMETER NETWORK?

A network consisting of elements that are not separable for analytical purpose is

known as distributed network.

Example: Transmission line.

13.DEFINE BRANCH?

A branch is a portion of a circuit with two terminals connected to it.

14.DEFINE NODE?

A node is a junction of two or more points. It is a point at which two or more

circuit elements are connected.

15.DEFINE LOOP?

A loop is any closed connections of branches.

16.WHAT ARE UNILATERAL AND BILATERAL NETWORKS?

BILATERAL NETWORKS:

A Circuit whose characteristics, behavior is same irrespective of the direction of

current through various elements is called unilateral network. Example: resistor consists

of resistor alone.

UNILATERAL NETWORKS:A Circuit whose characteristics, behavior is dependent

on the direction of current through various elements is called unilateral network.

Example: diode.

17.WHAT ARE LINEAR AND NON-LINAER NETWORK?

LINEAR NETWORK:A circuit or network whose parameters I.e elements like

resistance, inductance, capacitance are always constant irrespective of change in time,

voltage, temperature. Ohms law can be applied to such network.

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NON-LINAER NETWORK: A circuit or network whose parameters I.e elements like

resistance, inductance, capacitance change their values with change in time, voltage,

temperature. Ohms law can be applied to such network.

18.DEFINE GRAPH?

When all elements in a network are replaced by lines with circles of dots at both ends.

19.DEFINE TREE?

It is an interconnected open set of branches which includes all the nodes of the given

graph.

20.DEFINE IMPEDANCE AND ADMITTANCE?

Impedance: The ratio of phasor voltage to phasor current is called impedance

Z=V/I.

Admittance: reciprocal of impedance is called admittance (Y)

Y=I/Z.

21.DEFINE DUALITY?

In an electrical circuit itself there are pair of terms, which can be interchanged to

get new circuits.

22.WHAT IS AN ORIENTED GRAPHS?

A directed graph is called an oriented graphif it is the orientation of an undirected

graph.

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UNITII

NETWORK THEOREMS FOR AC AND DC CIRCUITS

1. STATE SUPERPOSITION THEOREM?

In a linear bilateral network containing two or more independent sources, the

voltage across or the current through any branch is algebraic sum of individual voltages

or currents produced by each independent source acting separately with all the

independent sources set equal to zero.

2. STATE RECIPROCITY THEOREM?

In any passive, linear, bilateral, single source network interchanging the position

of ideal voltage source and an ideal ammeter does not alter the ammeter reading (current)

and interchanging the position of current source and an ideal voltmeter does not alter

voltmeter reading (voltage).

3. STATE THEVENINS THEOREM?

Any linear active two terminal network containing resistance and voltage sources

and or current sources can be replaced by a single voltage sources V th in series with a

single resistance Rth.

The thevenin equivalent voltage Vth is the open circuit voltage at the networkterminals, and the thevenins resistance

Rth is the resistance between the network terminals when all sources are replaced

with their internal resistances.

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4. STATE NORTONS THEOREM?

Any linear active two terminals network containing resistance and voltage sources

and or current sources can be replaced by single current source INin parallel with a single

resistance RN.

The Nortons equivalent current IN is the short circuit current through the

terminals.

RN- resistance between the network terminals when all sources are replaced with

their internal resistances.

5.STATE MAXIMUM POWER TRANSFER THEOREM?

In a linear bilateral network containing an independent voltage source in series

with resistance Rsdelivers maximum power to the load resistance RL when RL= Rs.

Similarly the independent current source in parallel with source resistance Rs

delivers a maximum power to the load resistance when RL= Rs.

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5. STATE COMPENSATION THEOREM?

In a linear network any resistance R that carries a current I can be replaced by a

voltage source with emf V=IR with zero internal resistance.

Similarly if the voltage across the resistance is V then it can be replaced by a

current source I=V/R after replacement the current and voltages in all the other parts of

the network remain unchanged.

6. STATE MILLMANS THEOREM?

Consider N voltage sources V1, V2, -------VNin series with N resistors R1, R2, -----

--RN. Then according to Millmans theorem we can replace all the voltage sources and

resistance between terminals by a single voltage source V in series with a single

resistance R.

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1/R = G

7. STATE MAXIMUM POWER TRANSFER THEOREM? (AC CIRCUIT)

Maximum power will be delivered from a source to a load, when the load impedance

is equal to the complex conjugate of the internal source impedance.

8. STATE MILLMANS THEOREM? (AC CIRCUITS)

In any network, if the voltages V1, V2. Vn with internal impedances Z1, Z2

..Zn respectively, is in parallel then these sources may be replaced by a single voltage

source V in series with single impedance Z.

9. STATE TELLEGENS THEOREM?

In any network, the summation of instantaneous power or the summation of

complex power of sinusoidal sources is zero.

10. WRITE THE EQUATION FOR CONVERTING DELTA TO STAR?

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11.WRITE THE EQUATION FOR CONVERTING STAR TO DELTA?

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UNIT-III

COUPLED CIRCUITS, RESONANCE AND THREE PHASE

CIRCUITS:

1. DEFINE RESONANCE?

An AC circuit is said to in resonance when the input voltage and input current are

in phase. At Resonance the power factor of the circuit is unity and the circuit is purely

resistive.

2. WHAT IS THE CONDITION FOR SERIES RESONANCE?

XL=XC

If inductive reactance of a network equals capacitive reactance then the network is

said to be in resonance.

3. WHAT IS RESONANT FREQUENCY?

The frequency at which resonance occurs is called resonance frequency.

4.

WHAT ARE THE APPLICATIONS OF SERIES RESONANCE?

a) It is used to increase the signal voltage and current at desired frequency.

b) Used in some electronic circuits such as antenna circuits and tuning circuits.

5. DEFINE BANDWIDTH?

Bandwidth is defined as the band frequency between upper cut-off frequency

(f2) and lower cut-off frequency (f1).

BANDWIDTH= f2-f1 = R/2L.

6. DEFINE QUALITY FACTOR OR Q-FACTOR?

The quality factor is defined as the ratio of maximum energy stored to the energy

dissipated per cycle.

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It is also defined as ratio of bandwidth to the resonant frequency.

B= BANDWIDTH

7. DEFINE HALF POWER FREQUENCIES?

The frequencies at which the power is half the power at resonance are called half

power frequencies.

LOWER HALF POWER FREQUENCY f1 = f0R/4L

UPPER HALF POWER FREQUENCY f2 = f0+ R/4L.

8. WRITE THE CONDITION AT WHICH A PARALLEL RESONANCE

CIRCUITRESONATES AT ALL FREQUENCIES?

R1=R2=

9. DEFINE SELF INDUCTANCE?

It is defined as flux linkage in that coil per one ampere current in the same coil.

It also defined as Weber turns per ampere current in the coil. Unit is Henry.

10.DEFINE MUTUAL INDUCTANCE?

The mutual inductance between 2 coils is defined as Weber turns in one coil per

ampere current in other coil.

I

NL B

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It is also defined as the ability of one coil to produce emf in other coil by

induction when the current in the first changes.

11.DEFINE COEFFICIENT OF COUPLING (K)?

The fraction of the total flux produced by coil1 linking coil 2 is called of

coefficient of coupling.

12.WRITE THE RELATION BETWEEN M, K, L1 AND L2?

13.STATE DOT RULE?

If both currents enter dotted ends of couple coils or if both currents leave

dotted ends then the signs on the M-terms will be same as the signs on the L-terms.

If one current enters a dotted end and other an un-dotted end, then the signs on

the M-terms will be opposite to the signs on the L-terms.

14.WHAT IS SERIES AIDING CIRCUIT?

When the current enters both the coils at dotted terminal in a series circuit

then it is called as series aiding.

LEFF= L1+L2+2M.

15.WHAT IS SERIES OPPOSING CIRCUIT?

When the current enters the first coil at dotted terminal and leaves the other coil atdotted terminal in a series circuit then it is called as series aiding.

LEFF= L1+L2-2M.

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16. WHAT IS PARALLEL AIDING CIRCUIT?

When the current enters both the coils at dotted terminal in a parallel circuit, then it is

called parallel aiding circuit.

LEFF= L1L2-M

2

L1+L2-2M

17.WHAT IS PARALLEL OPPOSING CIRCUIT?

When the current enters the first coil at dotted terminal and leaves the other coil at

dotted terminal in a parallel circuit then it is called as series aiding.

LEFF= L1L2-M2

L1+L2-2M

18.DEFINE REAL POWER?

Real power is defined as the actual power consumed in AC circuit. It is denoted

by P. Unit is Watts

P=V I COS

V= RMS VALUE OF VOLTAGE

I= RMS VALUE OF CURRENT

= PHASE ANGLE BETWEEN V&I.

19.DEFINE REACTIVE POWER?

Reactive power is defined as the total power consumed by pure reactance (either

inductive or capacitive or both) in the AC circuit. It is denoted by Q. Its unit is volt

Ampere reactive (VAR).

Q=V*I Sin


I= RMS VALUE OF CURRENT

= PHASE ANGLE BETWEEN V&I.

20.DEFINE APPARENT POWER?

Apparent power is defined as the total power consumed in the AC circuit. It is

given by sum of real power and reactive power. It is denoted by S. Its unit is volt .

S=P+jQ or S=VI


I= RMS VALUE OF CURRENT.

21.DEFINE POWER FACTOR?

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Power factor is defined as the cosine of the angle between the input voltage and

input current.

P.F = COS.

(OR)

It is defined as the ratio of real power to apparent power

22.WHAT ARE LINE AND PHASE VOLTAGES AND WHAT IS THE

RELATION BETWEEN THEM?

Line voltage is defined as the voltage between any two lines of a 3 phasesystem. It is represented by EL.

Phase voltage is defined as the voltage between one line and the neutral

wire of the star connected system.

23.WHAT IS THE DIFFERENCEE BETWEEN SINGLE PHASE AND THREE

PHASE AC SUPPLY?

S.NO SINGLE PHASE AC SUPPLY THREE PHASE AC SUPPLY

1 It has one conductor It has three conductors

2 Low power applications High power applications

3 It has 2 line phases and neutralline for return path

It has three or four lines.R, Y, B , N(neutral)

P.F = REAL POWER

APPARENT POWER

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UNITIV

TRANSIENT ANALYSIS:

1.

WHAT IS TRANSIENT?

Transient is a short lived oscillations in a network caused by sudden change of

voltage or current or energy storage elements such as inductance and capacitance.

2. WHAT IS TRANSIENT STATE?

The behavior of the voltage or current when it is changed from one state to

another state is called transient state.

3. WHAT IS TRANSIENT TIME?

The time taken for the circuit to change from one steady state to anothersteady state is called transient time.

4. WHAT IS TRANSIENT RESPONSE?

The storage elements deliver their energy to the resistance, hence the response

changes with time and get saturated after sometime is referred as transient response.

5. WHAT IS NATURAL RESPONSE?

The response of the circuit due to stored energy alone without external source is

called natural response.

6. WHAT IS FORCED RESPONSE?

The response of the circuit due to without external source is called forced

response.

7. WHAT IS TOTAL RESPONSE?

TOTAL RESPONSE = NATURAL RESPONSE + FORCED RESPONSE.

8.

DEFINE TIME CONSTANT OF RL CIRCUIT?

The time taken to reach 63.2% of final value in a RL circuit is called time

constant of RL circuit.

Time constant T= L/R

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9. DEFINE TIME CONSTANT OF RC CIRCUIT?

The time taken to reach 36.8% of initial current in a RC circuit is called time

constant of RC circuit.

Time constant = RC.

10.DEFINE INITIAL VALUE THEOREM?

If f(t) and f(t) both are laplace transformable.

11.DEFINE FINAL VALUE THEOREM?

If f (t) and f (t) both are Laplace transformable.

12.WHAT ARE THE ADVANTAGES OF LAPLACE TRANSFORM?

It transforms the exponential and trigonometric functions into simple algebraic

functions.

a) It transforms differentiation and integration into multiplication an division.

b) It transforms integro-differential equations into algebraic equations.

c) It makes use of step and impulse response.

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UNITV

NETWORK FUNCTIONS AND PARAMETERS

1.

WHAT IS TRANSFER FUNCTION OF A CIRCUIT?

The transfer function of a circuit is defined as the ratio of laplace transform of the

output to the laplace transform of the input with the initial conditions are zero.

2. DEFINE POLES AND ZEROS OF A NETWORK?

The values of s at which the network function become zero are known as zeros.

The values of s at which the network function become infinity are known as

poles.

3. DEFINE DRIVING POINT IMPEDANCE?

It is defined as the ratio of voltage transform to the current transform at a given

port for a network with zero initial conditions.

4. DEFINE DRIVING POINT ADMITTANCE?

It is defined as the ratio of current transform to the voltage transform at a given

port for a network with zero initial conditions.

5. DEFINE VOLTAGE TRANSFER RATIO?

The ratio of output port voltage to input port voltage known as voltage transfer

ratio.

6.

DEFINE TRANSFER IMPEDANCE?

The ratio of output voltage to input current is called transfer function.

G(s) = V2(S)

V1(S)

Z11(s) = V2(S)

I1(S)

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7. DEFINE TRANSFER CURRENT RATIO?

The ratio of output current to the input current is called transfer current ratio.

8. DEFINE TRANSFER ADMITTANCE?

The ratio of output current to the input voltage known as transfer admittance.\

9.

WHAT ARE TWO PORT NETWORK?

A network that has two pairs of terminals is called two port networks.

10.

WHAT IS ONE PORT NETWORK?

A network has a pair of terminals is called one port network.

21(s) = I2(S)

I1(S)

Y11(s) = I2(S)

V1 S

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PREPARED BY N SHANKAR

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11.

DEFINE Z PARAMETERS?

It is also called as open circuit impedance parameters

12.DEFINE Y PARAMETER?

It is also short circuit admittance parameter

13.DEFINE H-PARAMETER?

Used for constructing models for transistor

14.DEFINE ABCD PARAMETER

It is also called as transmission parameters

eca 2 marks

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