Series & parallel circuits

Sounds familiar? On an old string of fairy lights, a single bulb breaks and suddenly the whole string goes dark. At home, on the other hand, you can switch off the kitchen light without the living room going dark. The difference lies in how the lamps are wired together.

Series circuit: one path for everything

In a series circuit, the lamps sit one after another on a single path. The current has to pass through all of them in turn, so the same current flows everywhere along that path. The voltage of the source, by contrast, is shared between the lamps: identical lamps all get the same share, half each with two lamps, a third each with three. That is why they shine dimmer than a single lamp would. And if one lamp breaks, the only path is interrupted: they all go out, exactly like on the old string of fairy lights.

Parallel circuit: each one gets everything

In a parallel circuit, each lamp has its own direct connection to the source. That way, the full voltage sits across every lamp and each one shines at full brightness. If one breaks, the current simply keeps flowing along the other paths. This is exactly how your home is wired: all devices hang in parallel at 230 V and work independently of each other.

Advantages and disadvantages compared

The series circuit needs little wiring and a single switch controls everything, but the lamps shine weaker and one defect shuts everything down. The parallel circuit needs more wiring, but every device gets the full voltage and can be switched on and off individually. That is why you find series circuits mostly in simple fairy lights and parallel circuits everywhere around the house.