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Overview
Series and parallel circuits are two fundamental ways to connect electrical components. In a series circuit, components are connected along a single path. In a parallel circuit, components are connected across shared junctions, creating multiple paths. These patterns determine how current and voltage behave.
Series Circuits
In a series circuit, the same current passes through each component because there is only one path for charge flow.
Parallel Circuits
In a parallel circuit, components are connected across the same two points. Each branch has the same voltage across it, while current divides among branches.
Equivalent Resistance
Equivalent resistance replaces a group of resistors with a single resistance that has the same effect on the circuit. Series resistances add directly, while parallel resistance is smaller than the smallest individual branch resistance.
Voltage in Series
In a series circuit, the source voltage is divided among components. The voltage drop across each component depends on its resistance.
Current in Parallel
In a parallel circuit, total current is the sum of branch currents. Each branch current depends on its resistance and the shared voltage.
Failure Behavior
If one component fails open in a series circuit, the whole path can stop working. In parallel circuits, other branches may continue operating.
Household Wiring
Many household circuits use parallel arrangements so devices can receive the same supply voltage and operate independently.
Common Mistakes
A common mistake is using series rules in a parallel circuit or parallel rules in a series circuit. The connection pattern must be identified first.
Why This Matters in Physics
Series and parallel circuits are foundational for electrical design, troubleshooting, electronics, power systems, and safety.