Have you ever tried to hang a string of lights for the holidays, only to find that the lights wouldn't work? A single broken bulb can make every light on the string go out. This is because electricity requires an unbroken circuit to travel through the wires and light the bulbs. When one bulb goes out, the circuit is broken, so none of the bulbs on the string can light up.
Why It Matters
Electricians avoid this pitfall by using something called a parallel circuit. In a parallel circuit, the electricity flows along two or more paths that do not cross. Thus, even if one path is broken, the others can continue to function.
You probably use parallel circuits every day. In fact, most of us take them for granted, which is why strings of lights are so frustrating. For instance, are there any lights in your home with more than one light bulb? What happens when one bulb blows out? If the others stay lit, the fixture has parallel wiring.
In most homes, the electricity coming into the building also is divided into parallel circuits. This way, when a fuse blows or a circuit breaker trips, only some of the rooms lose power. Parallel circuits limit the damage from breaks and outages.
See for yourself: https://www.youtube.com/watch?v=x2EuYqj_0Uk
Learn more about parallel circuits and their uses with the links below.