Basic DC Theory DC CIRCUIT TERMINOLOGYParallelCircuitParallel circuits are those circuits which have two or more components connected across thesame voltage source (Figure 17). Resistors R1, R2, and R3are in parallel with each other and thesource. Each parallel path is a branch with its own individual current. When the current leavesthe source V, part I1 of IT will flow through R1; part I2 will flow through R2; and part I3 will flowthrough R3. Current through each branch can be different; however, voltage throughout thecircuit will be equal.V = V1 = V2 = V3.Figure 17 Parallel CircuitEquivalentResistanceIn a parallel circuit, the total resistance of the resistors in parallel is referred to as equivalentresistance. This can be described as the total circuit resistance as seen by the voltage source.In all cases, the equivalent resistance will be less than any of the individual parallel circuitresistors. Using Ohm’s Law, equivalent resistance (REQ) can be found by dividing the sourcevoltage (V) by the total circuit current (IT), as shown in Figure 17.REQVItRev. 0 Page 21 ES-02
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