Series -Parallel Circuits

[Pages:33]6 Chapter

Series-Parallel Circuits

Topics Covered in Chapter 6 6-1: Finding RT for Series-Parallel Resistances

6-2: Resistance Strings in Parallel 6-3: Resistance Banks in Series 6-4: Resistance Banks and Strings in Series-Parallel

? 2007 The McGraw-Hill Companies, Inc. All rights reserved.

Topics Covered in Chapter 6

6-5: Analyzing Series-Parallel Circuits with Random Unknowns 6-6: The Wheatstone Bridge 6-7: Troubleshooting: Opens and Shorts in SeriesParallel Circuits

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? 2007 The McGraw-Hill Companies, Inc. All rights reserved.

6-1: Finding RT for Series-Parallel Resistances

Overview of Series-Parallel Circuits

A series-parallel circuit, or combination circuit, combines both series and parallel connections. Most electronic circuits fall into this category. Series-parallel circuits are typically used when different voltage and current values are required from the same voltage source.

Series components form a series string.

Parallel components form a parallel bank.

6-1: Finding RT for Series-Parallel Resistances

Overview of Series-Parallel Circuits

1

3

V

2

There are three branches in this circuit; sections 1 and 2 are series strings.

6-1: Finding RT for Series-Parallel Resistances

Overview of Series-Parallel Circuits

1

V

3

2

There are three series sections in this circuit; sections 1 and 2 are parallel banks.

6-1: Finding RT for Series-Parallel Resistances

To find RT for a series-parallel circuit, add the series

resistances and combine the

parallel resistances.

In this diagram, R1 and R2 are in series, and R3 and R4 are in parallel. However, R2 is not in series with the parallel

resistances: Resistances in

series have the same current,

but the current in R2 is equal to the sum of the branch

currents I3 and I4.

Fig. 6-1b: Schematic diagram of a seriesparallel circuit.

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6-1: Finding RT for Series-Parallel Resistances

For Fig. 6-1b,

The series resistances are:

0.5k + 0.5k = 1k

The parallel resistances are:

1k / 2 = 0.5k

The series and parallel values are then added for the value of RT:

1k + 0.5k = 1.5 k

6-2: Resistance Strings in Parallel

In this figure, branch 1 has two resistances in series; branch 2 has only one resistance. Ohm's Law can be applied to each branch, using the same rules for the series and parallel components that were discussed in Chapters 4 and 5.

Fig. 6-3a: Series string in parallel with another branch (schematic diagram).

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