Current in Series and Parallel Circuits
Electric current behaves differently in series and parallel circuits. Understanding how current is distributed helps you design circuits, calculate component values and troubleshoot electronic equipment.
Current in Series Circuits
In a series circuit, all components are connected one after another, forming a single path for current to flow.
Because there is only one path, the same current flows through every component.
For example, if a battery supplies 2 amperes to a series circuit, every resistor, switch, LED and lamp in that circuit carries exactly 2 amperes.
Example of a Series Circuit
| Component | Current |
|---|---|
| Battery | 2 A |
| Switch | 2 A |
| Resistor R₁ | 2 A |
| Resistor R₂ | 2 A |
| LED | 2 A |
Every component carries the same current because there is only one route for electrons to travel.
Current in Parallel Circuits
In a parallel circuit, current has more than one path available.
The total current supplied by the source divides among the different branches.
The amount of current flowing through each branch depends on its resistance.
Current Division
Current naturally prefers the path with the lowest resistance.
Branches having lower resistance carry larger currents, while branches with higher resistance carry smaller currents.
The sum of all branch currents always equals the total current supplied by the source.
Example of a Parallel Circuit
| Branch | Current |
|---|---|
| Battery Output | 5 A |
| Branch 1 | 2 A |
| Branch 2 | 1.5 A |
| Branch 3 | 1.5 A |
2 A + 1.5 A + 1.5 A = 5 A
Kirchhoff's Current Law
Kirchhoff's Current Law states that the total current entering a junction is equal to the total current leaving that junction.
In other words, electric charge is conserved.
At every junction:
Current In = Current Out
Series vs Parallel Current
| Series Circuit | Parallel Circuit |
|---|---|
| Current is the same everywhere. | Current divides between branches. |
| One current path. | Multiple current paths. |
| Voltage divides. | Voltage is the same across every branch. |
Practical Examples
| Application | Circuit Type |
|---|---|
| LED Strip Segments | Series |
| Christmas Light Chains | Series |
| House Wiring | Parallel |
| Automobile Electrical System | Parallel |
| Power Distribution Boards | Parallel |
| Speaker Crossover Networks | Series & Parallel Combination |
Common Mistakes
- Assuming current is always the same in every circuit.
- Confusing current division with voltage division.
- Ignoring the effect of branch resistance.
- Forgetting that current is conserved at junctions.
Key Points
- Series circuits have only one current path.
- The same current flows through every series component.
- Parallel circuits divide current between branches.
- The total branch currents equal the source current.
- Lower resistance branches carry more current.
- Kirchhoff's Current Law applies to every junction.