Components of an electrical circuit can be connected in many different ways. The two simplest of these are called series and parallel and occur frequently. In this lesson, you will learn the difference between series and parallel circuits.

A circuit is a path that controls the flow of electricity. In most electrical circuits, the path that the electricity follows is made up of solid metal wires.

A circuit usually includes a conductor (metal wires), an energy source (e.g., a battery), a switching mechanism to open and close the circuit, and a load. A load is a device that converts electrical energy into another form of energy.

   

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The easiest way to learn about circuits is to learn how to read circuit diagrams. Circuit diagrams have various symbols that represent each part of a circuit. Below are some of the most common.

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Below is a simple diagram of a light (an X inside the circle) connected to a single cell and a switch. On both the single cell symbol and the battery symbol, the power flows from the larger line. In this case, the larger line is on the right, so the power in this diagram flows clockwise around the diagram. Also, notice that the switch is open, so the light will not be on.

 

   

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Notice how the electricity has to flow through all three bulbs before returning to the battery. If one of the bulbs burns out, none will work.

Another problem with series circuits is that as you add more bulbs to the series, the resistance increases. This means the current has more difficulty travelling along the path. As the resistance increases, all the bulbs become dimmer.

However, there is an advantage to using a series circuit. In some household circuits, switches are wired in series with other components, such as wall plugs and lights, so that you can turn on or off all the electricity in a room with the flick of a switch.

However, you may not want to have everything in an area controlled by one switch. Remember, if an area is wired as a series circuit, anything not working on that circuit stops everything else from working. What if your freezer depended on the light in the room to continue to work? If the light was off, your frozen food would thaw and spoil!

Parallel Circuits

That is why most of your house is wired in parallel circuits that have a separate current path for each section of the circuit. Then, if one thing on the circuit is not working, the other objects on the circuit are not affected.

 

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The diagrams above each show three lights. Notice how they all have their own pathway for the electricity to follow. If the light on the left burns out, it has no effect on the other two lights; they will continue to work.

Another interesting thing about parallel circuits is that the more objects you add to a parallel circuit, the better it works. Unlike the series circuit where the pathway became more resistant with more items, the pathway in a parallel circuit becomes less resistant with more items. Why is that possible? It's simple: The more items you have on the circuit, the more paths there are for the current to flow! Is it easier to drink a milkshake through one straw or two? Two obviously! You have more paths for the milkshake to get to your mouth. You have lowered the resistance.