Introduction of Electrical Circuit

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DENT 1233 ELECTRICAL CIRCUIT

CHAPTER 1 : REVIEW ON BASIC LAWS


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BASIC CONCEPTS

INTRO CIRCUIT ELEMENTS

SYSTEM REPRESENTATION

IDEAL & NON-IDEAL SOURCE

BRANCH

NODE

LOOP


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INTRO

Electric Circuit(D.C and A.C) is aninterconnection of electrical components to

perform certain function.

Examplesof electrical components areresistor, capacitor, inductor, battery, A.C source,

etc.


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CIRCUIT ELEMENTS

Active element Voltage/current source that can deliver energy to

the network

Example :- generators, batteries, operational

amplifiers

Most important are voltage or current sources

generally generate power to the circuit connected


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CIRCUIT ELEMENTS

Independent sources Voltage sourcesmaintains a

voltage(fixed or varying in time)

which is not affected by any other

quantity

Current sourcesmaintains a

current(fixed or time-varying) which

is unaffected by any other quantity

Dependent sources

Voltage and current sources which is

their values varying with some other

variables


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CIRCUIT ELEMENTS

Dependent sources Voltage/current varies according to other variables (current or

voltage) connected in the circuit

Diamond shape symbol


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CIRCUIT ELEMENTS Passive element Absorb/store energy from the source

Example :- resistors(R), inductors(L),

capacitors(C)


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SYSTEM REPRESENTATION

Electrical energy sources (active elements)deliver/provide power to the loads (passive elements)

Positive current (proton) flows from positive terminal

Electrical system representationconceptual, symbolic

(circuit) and physical


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IDEAL VOLTAGE SOURCE

An ideal source is a source that delivers a constant/certain amount of energy. The amount of voltage/ current

delivers does not change due to circuit connection

An ideal voltage source delivers certain amount of voltage

across its terminal independently to the current flowingthrough it. The amount of current delivers by the source

is determine by the circuit connection


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IDEAL CURRENT SOURCE

Delivers certain amount of current to any circuitconnected to it. The voltage in the circuit determined by

the circuit connected to it

Have property such that the current deliver is

independence to the voltage across its load


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NON IDEAL SOURCE

In practice, usually all sources consists of internalresistance, rs

Non ideal voltage source consists of an internal resistance in

series with an ideal voltage source, hence there is a voltage

drop

Non ideal current source consists of an internal resistance in

parallel with an ideal current source, hence the current flow

will be reduced


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BRANCH

Any part of circuit that consist of 2 or more terminalsacross it

Represents a single element such as a voltage source or a

resistor etc


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NODE

Point where two or more components (branches) areconnected

An area that enclose or combined more than one node

called as SUPERNODE


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LOOP

Any closed or complete connection of branches


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BASIC LAWS

OHMS LAW KIRCHHOFFS LAWS

KIRCHHOFFS VOLTAGE LAW (KVL)

KIRCHHOFFS CURRENT LAW (KCL)


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OHMS LAW

Stated that, The voltage V across a resistor is directly proportional to the

current Iflowing through the resistor


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OHMS LAW

Example :- Find the current in the following circuit ;


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KIRCHHOFFS VOLTAGE LAW

Stated that, The algebraic sum of the voltages around any closed path

(loop) must be zero

OR

The sum of all the voltage drops around a single closed path in

a circuit is equal to the total source voltage in that closed path

SUM OF VOLTAGE DROPS = SUM OF SOURCE VOLTAGE


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Example :- Find the values of vcand ve


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KIRCHHOFFS CURRENT LAW

Stated that, The algebraic sum of the current at a node (entering or

leaving) is zero

OR

The sum of currents entering a node equals the sum of the

currents leaving a node

SUM OF CURRENT ENTER = SUM OF CURRENT LEAVE


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The algebraic sum of the four currents entering the node must

be zero

The algebraic sum of the four currents leaving the node must

be zero

Sum of the currents going into a node must equal the sum of

the currents leaving or going out from a node


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Example :- Calculate the current I1, I2and I3


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VOLTAGE DIVIDERS

The voltage drop across any resistor or combination ofresistors in a series circuit is equal to the ratio of that

resistance value to the total resistance, multiplied by the

source voltage


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CURRENT DIVIDERS

The total current divides among parallel resistors intocurrents with values inversely proportional to the

resistance values

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Introduction of Electrical Circuit