What is a series circuit?

Short Answer

A series circuit is a type of electrical circuit in which all the components are connected one after another in a single path. In this arrangement, the same current flows through every component because there is only one route for the electric charges to move.

If one component in a series circuit stops working, the entire circuit breaks. The total resistance in a series circuit is the sum of all individual resistances. Series circuits are commonly used in small devices like decorative lights and simple electrical systems.

Detailed Explanation

Series circuit

A series circuit is one of the basic arrangements used in electrical and electronic systems. In a series circuit, components such as resistors, bulbs, or cells are connected in a single path, without any branching. This means the current has only one route to flow. Because of this single path, the properties of the circuit—such as current, resistance, and voltage distribution—follow specific rules that are easy to understand and apply. Series circuits are widely used in simple electric devices and learning about them is essential for understanding electric current behavior.

Structure of a series circuit

In a series circuit:

  • All components are connected end to end.
  • There are no junctions or branches.
  • The current flows through each component one after another.

For example, if three bulbs are connected in series, the current will pass through bulb 1, then bulb 2, and finally bulb 3. If any bulb fails, the entire circuit stops working because the path is broken.

Current in a series circuit

One of the most important properties of a series circuit is that the current remains the same through all components.

This happens because:

  • The current has only one path.
  • The same number of electrons pass through each component per second.

So, if the current flowing from the battery is 2 A, then every resistor or bulb in the series circuit will also have a current of 2 A.

This is why Christmas lights connected in series all glow equally—because each one receives the same current.

Resistance in a series circuit

The total resistance in a series circuit is the sum of all the resistances.

R(total) = R₁ + R₂ + R₃ + …

Because resistances add up, the total resistance of the circuit increases with every new component added. As resistance increases, the current decreases for the same applied voltage.

This is why adding more bulbs in series makes them glow dimmer—because the total resistance is higher.

Voltage in a series circuit

In a series circuit:

  • The total voltage of the supply distributes or divides across the components.
  • The voltage drop across each component depends on its resistance.

For example, if a 12 V battery is connected to two resistors in series, the voltage drops might be:

  • 6 V across the first resistor
  • 6 V across the second resistor

The total adds to 12 V, which follows Kirchhoff’s Voltage Law.

Power in a series circuit

Each component uses electrical energy according to the power formula:

P = VI

But since current is the same for all, the power depends on the voltage drop across each component. Components with larger resistance have a larger voltage drop and therefore consume more power.

Advantages of a series circuit

  1. Simple design
    Easy to set up and understand.
  2. Low wiring cost
    Fewer wires needed compared to parallel circuits.
  3. Equal current distribution
    All components receive the same current.

Disadvantages of a series circuit

  1. If one component fails, the circuit breaks
    This is why series decorative lights turn off completely if one bulb burns out.
  2. Voltage divides among components
    This may reduce the brightness of bulbs.
  3. Higher total resistance
    More components mean more resistance, reducing current.

Examples of series circuits

  1. Torch lights:
    Cells inside a torch are usually connected in series to increase voltage.
  2. Decorative lights (old type):
    If one bulb fails, the entire string turns off.
  3. Simple classroom experiments:
    Students connect bulbs or resistors in series to understand current flow and voltage division.
  4. Batteries in series:
    Connecting two 1.5 V cells in series gives 3 V, providing more energy for devices.

Series combination of cells

Cells connected in series have:

Total EMF = E₁ + E₂ + E₃

This increases the total voltage and is useful in devices that need higher power.

Understanding series circuits in daily life

Many household items use series circuits internally for simple control, such as:

  • Switches controlling bulbs
  • Toys with series-connected batteries
  • Doorbells

Although modern appliances use more complex wiring, the basic idea of series connection remains important.

Conclusion

A series circuit is an arrangement where electrical components are connected in a single path, allowing the same current to flow through each component. The total resistance increases with more components, and the voltage divides across them. Series circuits are simple, easy to build, and useful in many basic electrical applications. Understanding series circuits helps in learning how electricity flows and how different components behave when connected in a sequence.