Series Circuits

Series Circuits

Imagine several components placed along one road.

Charge has only one route, so the same current passes through every component.

Adding more resistors makes the route harder for current.

Series Circuits

A series circuit is a circuit in which components are connected one after another in a single conducting path.

Because there is only one path for charge to move through, the same current passes through every component in a series circuit.

Current in Series

For components connected in series:

**I = I₁ = I₂ = I₃**

The current does not split because there is no junction providing another path.

Potential Difference in Series

The total potential difference supplied by the source is shared among the components:

**Vₜ = V₁ + V₂ + V₃**

A component with a greater resistance receives a greater share of the total p.d. when the same current flows through all components.

Resistance in Series

The total resistance is:

Rₜ = R₁ + R₂ + R₃ + ...

Adding another resistor in series therefore increases total resistance.

From Ohm's law:

**I = VR**

If supply voltage remains constant while total resistance increases, the circuit current decreases.

Example

Three resistors of 2 Ω, 3 Ω and 5 Ω are connected in series.

**Rₜ = 2 + 3 + 5**

**Rₜ = 10 Ω**

If connected to a 20 V source:

**I = VR**

**I = 2010 = 2 A**

The same 2 A passes through all three resistors.

What Happens if One Component Breaks?

If one component breaks and creates an open circuit, the only conducting path is interrupted.

Current therefore stops throughout the circuit.

Series Circuits — Advanced

For a series network, charge conservation requires identical current through each element. Kirchhoff's voltage principle gives the sum of component voltage drops equal to the source voltage.

For resistors:

**R_eq = ΣR**