Characteristics of Parallel Circuits
A Fundamental Building Block of Electronic Circuits
Purely parallel circuits are circuits in which each current path is connected across the source. It comprises a source, circuit control, multiple loads and multiple current paths. Each load, or current path, feels the full potential (voltage) of the source. Though the source sees only one load (effectively), each parallel branch works like a separate series circuit.
When comparing the characteristics of parallel circuits to series circuits the primary difference is current flow. Series circuits have only one path of current from the source, through the components, and back to the source. If one of the components should fail, the circuit will cease to function. Parallel circuits are designed with multiple paths of current flow, which allows each branch to work independently. Should any of the parallel branches of the circuit fail, other branches may still function normally.
Advantages of Parallel Circuits
One advantage of the parallel circuit has already been described; multiple current paths. Having multiple current paths also provides the advantage of being able to control each load (i.e. switch on/off) or a group of loads.
Controlling Current Flow in a Parallel Circuit
Controlling current flow within a parallel circuit can be accomplished in several ways. A switch in series with the source, as shown in Figure 1 (below) is used to open the current path for the entire circuit. A switch could be added to any of the individual branches to control current flow in that branch, as shown in Figure 2. Figure 3 shows a switch that controls current flow in Branches 3 and 4. This versatility allows the circuit designer a variety of options for circuit/load manipulation.
Analyzing a Parallel Circuit
When analyzing a purely parallel circuit each branch can be considered an individual series circuit, since each branch is connected across the source. Each branch will have it's own current, based on the size of the load (resistance to current flow) and the source voltage. Since voltage remains constant across each branch, checking for current flow in each branch will quickly reveal any problems within the circuit. An open branch will have no current flow, and current within the other branches will remain the same. A short in a branch would result in all current passing through that branch, while current will drop to zero (effectively) in the other branches, since current seeks the path of least resistance.
Utilizing parallel circuits, the designer has the ability to power several branches of a circuit with a single source voltage. It’s simple design makes it one of the fundamental building blocks of circuit design.
Source: Iowa State University, Center for Nondestructive Evaluation, NDT Resource Center
Figure 1 - Parallel circuit
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Figure 2 - Added switch controls branch
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Figure 3 - Added switch controls 2 branches
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