We are well acquainted with the word “series” as it is used in general life. The World Series is a succession of baseball games to decide the championship. A series of numbers is a succession of numbers. In Radio when we speak of series circuits, we mean the arrangement of apparatus in succession, one after the other, in such a way that the current must flow through one before it flows through the others. In series circuits, if one part is defective and current can’t pass through it, the entire circuit is opened. And this is the chief characteristic of series circuits--every part in that circuit is dependent on the other parts and every part must be intact, current must go through it, otherwise current cannot flow in the circuit.
Figure 10 shows a closed series circuit consisting of three cells connected in series with three resistances, R1, R2, R3 and a switch (S). The cells are connected in series--the positive terminal of each cell is joined with the negative terminal of the next cell in the series.
Fig. 10
As you learned in a previous lesson, the total e.m.f. acting in this circuit with the switch closed will be the sum of the e.m.f.’s of the individual cells.
The total resistance of the three resistance loads in series is the sum of individual resistances, that is R1 + R2 + R3.
CHARACTERISTICS OF PARALLEL CIRCUITS
Sources of e.m.f. are said to be connected in parallel when their positive terminals are joined to one conductor and their negative terminals to the other. Parallel connections of dry cells were shown in the previous lesson text. Another way of describing a parallel connection of dry cells is to say that all their positive poles are connected together and all their negative poles are connected together.
When loads are connected in parallel, each carries only part of the total current. Instead of having one main circuit as in a series circuit, in parallel circuits we have one main circuit and
