6.

Series-Parallel Circuits

In the previous discussions, series and parallel circuits have been

considered separately. The technician will encounter circuits consisting of

both series and parallel elements. A circuit of this type is referred to as

a combination circuit.

Solving for the quantities and elements in a

combination circuit is simply a matter of applying the laws and rules

discussed up to this point.

a. *Solving Combination-Circuit Problems. * The basic technique used for

solving combination-circuit problems is the use of equivalent circuits. To

simplify a complex circuit to a simple circuit containing only one load,

equivalent circuits are substituted (on paper) for the complex circuit they

represent.

The procedures for working these type of problems were covered in paragraph

5a(5), on page 87, and will not be repeated here.

b. *Redrawing Circuits for Clarity. * You will notice that the schematic

diagrams that you have been working with have shown parallel circuits drawn

as neat square figures, with each branch easily identified.

In actual practice, the wired circuits and more complex schematics are

rarely laid out in this simple form. For this reason, it is important to

recognize that circuits can be drawn in a variety of ways, and to learn some

of the techniques for redrawing them into their simplified form.

When a

circuit is redrawn for clarity or to its simplified form, the following

steps are used:

Step 1: Trace the current paths in the circuit.

Step 2: Label the junctions in the circuit.

Step 3: Recognize points which are the same potential.

Step 4: Visualize a rearrangement, "stretching" or "shrinking" of connecting

wires.

Step 5: Redraw the circuit into simpler form (through stages if necessary).