1

ELECTRICAL TECHNOLOGY EET 103/4

Explain and analyze series and parallel circuits

Explain, derive and analyze Ohm’s Law, Kirchhoff Current Law, Kirchhoff Voltage Law, Source Transformation, Thevenin theorem.

2

(CHAPTER 8)

METHOD OF ANALYSISMETHOD OF ANALYSIS

SOURCE CONVERSIONSOURCE CONVERSION

3

8.2 Current Sources The current source is often described

as the dual of the voltage source. A battery supplies a fixed voltage, and the

source current can vary; but the current source supplies a fixed current to the branch in which it is located, while its terminal voltage may vary as determined by the network to which it is applied.

4

8.2 Current Sources

5

8.2 Current SourcesA current source determines the current

in the branch in which it is located The magnitude and polarity of the

voltage across a current source are a function of the network to which it is applied

6

8.2 Current Sources

7

8.2 Current SourcesExample 8.1

Find Vs, V1 and I1:

8

8.2 Current SourcesExample 8.1 – solution

mA 101 II

111 RIV

33 10201010

V 200

V 2001 VVs

9

8.2 Current SourcesExample 8.2

Find Vs, I1 and I2:

10

8.2 Current SourcesExample 8.2 – solution

V 12EVs

V 12EVR

A 34

122

R

VI R

A 43721 III

11

8.3 Sources Conversion

An ideal source cannot be converted from one type to the other.

All practical sources – whether they are voltage or current – have some internal resistance.

12

8.3 Sources Conversion

Practical voltage source Practical current source

13

8.3 Sources Conversion

The equivalence between a current source and a voltage source exists only at their external terminals.

A source and its equivalent will establish current in the same direction though the applied load.

14

8.3 Sources Conversion

15

8.3 Sources ConversionExample 8.4

(a) Determine IL.(b) Convert the voltage source

to a current source.(c) Using the current source in

(b), calculate the current through RL.

16

8.3 Sources ConversionExample 8.4 – solution

LsTL RR

E

R

EI

A 142

6

17

8.3 Sources ConversionExample 8.4 – solution (cont’d)

IA 3

2

6

sR

EI

18

8.3 Sources ConversionExample 8.4 – solution (cont’d)

Voltage source Current sourceconverted to

19

8.3 Sources ConversionExample 8.4 – solution (cont’d)

Voltage source and its equivalent current source with the same load

20

8.3 Sources ConversionExample 8.4 – solution (cont’d)

Lp

pL RR

RII

A 142

23

21

8.3 Sources ConversionExample 8.5

Determine I2:

22

8.3 Sources ConversionExample 8.5 - solution

Convert the current source to a voltage source

Note the polarityV 1234111 RIE

23

8.3 Sources ConversionExample 8.5 – solution (cont’d)

Reconnect the voltage source E2 and its resistance R2:

V 1751221 EEET

52321 RRRT

A 4.35

172

T

T

R

EI