kvs baisc circuit analysis.pdf

8/22/2019 kvs baisc circuit analysis.pdf

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:BasicCircuitAnal sis

r. . . r vas avaDept. of Electrical Engineering

IIT Kanpur

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Objectives

1. Solve circuits (i.e., find currents and voltages of interest)b combinin resistances in series and arallel

2. Apply the voltage-division and current-division principles

3. Solve circuits by the node-voltage technique

4. Solve circuits by the mesh-current technique

5. Find Thvenin and Norton e uivalents and a l sourcetransformations

.

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Simplification Techniques

As engineers we like to be efficient : achieve the objective withminimum effort.

iis

Concept of equivalent circuits

Two circuits are equivalent if they have the same current-voltage behavior

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Analysis using REUSE methodology

Analyze, Remember and Reuse

o not carry out anays s rom scratc

Exam le: we do not carr out multi lication from scratchusing repeated addition !

10 2

x 3 3 x 4 = 12

You cannot carry out4 x 1 = 4

4 x 2 = 8

4 x 3 =12

Memorize multiplicationtable and use it again and

ease using the first principle 4 x 4 = 16

....................

aga n

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Creative Reuse !

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eve op equ va en c rcu s y com n ng severa

resistors into a single equivalent resistor

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Series Resistances

Both circuits are equivalent as far as v vs. i relation is concerned.7


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Parallel Resistances

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Example

Use conce t of series and arallel resistances to sim lif

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Example Use concept of series and parallel resistances to simplify

2 1

2

2 1

Re q

e q

e q

R RR R

=

+

R R R R R= + +

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1. Begin by locating a combination of resistances that are in

Circuit Analysis Using Series/Parallel Equivalents

seres or para e . ten t e pace to start wt s t e art estfrom the source.

2. Redraw the circuit with the equivalent resistance for thecombination found in step 1.

3. Repeat steps 1 and 2 until the circuit is reduced as far as

possible. Often (but not always) we end up with a single sourcean a s nge res stance.

4. Solve for the currents and volta es in the final e uivalent

circuit. Then go back one step and solve for unknown voltagesand current.

5. Repeat step 4 until the required current or voltage in the originalcircuit is found. 12


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Example

+n currentin R3 60V

-

+

3A

3A60V

-

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Find all the currents

V2Solve fori2, i3 and i4

-

+

V2

-

1 2 3 4R e q R R R= 2 1 1R e q e qR R= +

o ve or 1o ve or 2

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Voltage division

A volta e a lied to resistors connected in series will bedivided among them

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Example

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2R

21 RR +

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Current Division

The total current flowin into a arallel combination ofresistors will be divided among them

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Example

Find v usin volta e division and then find i and use it to findi3 using current division

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Use current division rule to find i1

Suppose we want to find i2 also

eq

i2

1

1

e q s

e q

Ri i

R R

=

+

32

2 3

e qi i

R R

=

+ 21

kvs baisc circuit analysis.pdf

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