What are parallel circuits?

November 10, 2014

A little bit of knowledge about electricity is a good thing to have. Here’s a primer on understanding the difference between a parallel circuit and a series circuit.

What are parallel circuits?

Q: What are parallel circuits?

A: When two electrical devices are connected into a circuit that is supplying energy, they can be connected in one of two ways: in a series or in a parallel.

  • As they sound, parallel circuits are when components are connected in parallel and the voltage (a.k.a. the electrical charge pushing the current) passing through each element is equal—though the current (how fast the electrical charge goes past the circuit) going through each element may not be equal.
  • Because currents like to take the path that’s easiest, elements with more difficult paths carry less current than elements with easier paths.

Q: So how does this apply to me?

A: Say you’re looking to put up a string of lights on your backyard patio.

  • In one string, there are several lights connected together in a circuit.
  • If they are connected in series, then an individual charge would go through each of the light bulbs continuously, so it has only one path and one series to follow.
  • If that path were disrupted, then the current would stop flowing and all the devices connected in that circuit would stop working.

If they are hooked up in a parallel circuit, one single charge would go through the external circuit and pass through one of the light bulbs. So here if that same path is broken, the electrons would just take another route to continue along.

Q: Can you explain it to me in an analogy?

A: Sure. One common analogy to explain parallel circuits is the “tollbooth analogy.”

  • Say you have a highway with a tollbooth. The one tollbooth is slowing down the flow of cars on the busy highway.
  • To alleviate the flow of traffic, authorities could add a series of tollbooths (series) so that you have to stop repeatedly to pay 25 cents at three different booths.
  • Adding tollbooths will boost the resistance to traffic and slow down your car flow rate (current).

Or you could expand your tollbooths via a parallel system, so you open up two more tollbooths beside the first and in total have three tollbooths side by side, providing the flow of cars with one of three possible throughways.

  • It would increase the amount of resistance facing traffic and boost the car flow rate.

*Not only is it dangerous, it may even be illegal in some provinces, such as Québec, to do your own electrical wiring. The solution: consider hiring a master electrician.

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