Series and Parallel Circuits

By Perry Henderson

Circuits come in two primary configurations and those are series and parallel. The electronics practitioner will see these circuit types for as long as they are engaged in working with electrical systems or electronics, so it is important to gain a solid understanding of how they work and where they are utilized. The configuration of the circuit will have significant effect on how the variables of current, voltage, and resistance will operate within the circuit. To become great at electronics a solid grounding in the basics is necessary to develop functional electronics.

To start with the easier of the two circuit types, series circuits are circuits where the components are attached end to end in a line or singular path. This single path allows for current to flow from component to component. The same current will pass through each electronics component, BUT the voltage will be divided between them. A parallel circuit will attach components across the identical same two points. This generates many pathways for current to flow. The voltage across each branch is identical, BUT the current divides depending on the resistance present with each pathway.

These two systems of circuit configuration each have their pluses and minuses. Series circuits for the most part are much simpler, and Christmas lights are probably the best example of this. Parallel circuits in many ways offer greater system robustness, the multiple pathways allow for systems or components to continue operation if there is a failure somewhere in the circuit. Parallel circuits are going to be seen more in industry and in homes. Understanding these two types of circuits helps in designing, predicting, and troubleshooting electronics.

Series Circuit Mathematical Formulas

Total Resistance (R total)
   R total = R₁ + R₂ + R₃ + … + Rₙ

Total Voltage (V total)
   V total = V₁ + V₂ + V₃ + … + Vₙ

Current (I) Identical through all components
   I = V total / R total

Parallel Circuit Mathematical Formulas

Total Resistance (R total)
   1 / R total = 1 / R₁ + 1 / R₂ + 1 / R₃ + … + 1 / Rₙ

Voltage (V) Identical across all branches
   V = V₁ = V₂ = V₃ = … = Vₙ

Total Current (I total)
   I total = I₁ + I₂ + I₃ + … + Iₙ

The Amateur Electrical Engineer