Chapter 13 SOLVING THE PARALLEL CIRCUITS

Chapter 13
SOLVING THE PARALLEL CIRCUITS

13.1 Parallel Circuit Connection

A parallel circuit is one in which all the loads are connected across the two voltage source lines. Each load acts independently of the other. This connection results in as many pathways for the current as there are load components connected in parallel.

13.2 Parallel Circuit Current, Voltage and Resistance Characteristics

Current  The total current in a parallel circuit is divided among each of the loads. Each load is connected directly across the supply lines and acts independently of the other loads, as far as current is concerned. The amount of current drawn by each load is determined by the resistance value of each load. The higher the resistance of the loa, the lower the amount of current taken.

Voltage  The voltage across each load connected in parallel is the same and is equal in value to that of the voltage source. This is due to the fact that each load is connected directly across the two line wires.

Resistance  The total resistance of a parallel circuit is less than the resistance of the smallest load resistance. When you connect loads in parallel you have more paths through which the current can flow. This results in less total opposition to the total current flow and a decrease in total resistance.

13.3 Solving Parallel Circuits

The procedure to follow in solving parallel circuit values of voltage, current and resistance is similar to that used for solving series circuits. Ohm’s law as it applies to the circuit as a whole and the individual loads is used. In addition, the parallel circuit characteristics of voltage, current and resistance must also be used. The parallel circuit characteristic expressed in the form of equations are as follows:   
                                                            IT =I1 + I2 + I3 …

                                                            VT = V1 = V2 = V3

                                                            RT =   R1 x R2              (for 2 loads)
                                                                      R1 + R2

                        1
RT =    1           1          1       (more than 2 loads)
           R1         R2        R3