How Does A Three-Pronged Plug Actually Work?

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Hey, folks!  

Captain Obvious has arrived, and today I have a lesson for you about three-pronged power outlets and how they work.  

These power outlets provide power to most of the electric devices in our homes, and the more we use them, the higher our bills will be! 


Not all of our devices run off of these power outlets these days, but many still do, such our lamps, night lights, laptops, blenders, as well as larger things like freezers, and televisions, to name just a few.

Below is a picture of a typical three-pronged plug that you find at the end of many electrical devices…

three pronged power plug

Even the least-technical of us knows what to do with one of these three-pronged plugs.

…Yep, we plug ’em into a three-holed power outlet and this sends power to our device or appliance.  “Wow, mind blown, thanks Captain Obvious!”  You’re welcome!  

Now, hold on…Have you ever really looked closely at one of these three-pronged power outlets…?

wall outlet with three holes

If you took high school electronics, you’re probably long gone by now, but to whoever is still reading, you can see that these holes are each slightly different.  

To state the obvious (that’s my job), the top left hole is slightly larger than the right hole, but otherwise they look the same in terms of shape.  

The middle hole underneath is a different shape – rounded at the top and flat on the bottom, as well as wider than both of the two top holes put together.  

Most of our power outlets in our homes look like this one, right down to the white plastic covering that is attached to prevent you, your kids, or your pet from fiddling with the wiring that is behind that covering.  

FYI, plastic does not conduct electricity (at least not very well), which is why its used to insulate wires, and also cover up wall sockets.

The Captain Says: Don’t Mess With The Holes!

Fiddling around with those differently shaped holes can result in getting zapped AKA electrocuted, as you may know from first hand experience.  

Here is a video showing what you should NOT do when it comes to electrical outlets, eg. stick metal objects into them.  **WARNING: Do not try this at home**

When you stick metal into these top two holes, you’re completing the circuit needed for power to flow, which is why you want to avoid making your body part of this circuit.

If you are powering your laptop or some other electrical device using a three-pronged plug, then fine, go right ahead complete the circuit.  

Otherwise, if you’re just playing around by sticking other things into these holes, you might just get yourself zapped because now YOU are part of the circuit and your body is not meant to conduct electricity.

To be clear, electricity is flowing through your home all the time, and is waiting to be used when you plug the appropriate plug into the appropriate outlet, thanks to the source of the power, which is most likely a nearby power plant like this one.

power plant

Your standard three-pronged outlet (also called a receptacle) can conduct up to 120 volts of electricity, and consists of the slot (also called a terminal) on the top right which connects to the “live” or “hot” wire, and then there’s the top left slot which connects to the neutral wire, and finally the bottom hole which connects to the ground wire, like so…

electrical outlet diagram

The circuit is completed when power runs through the live slot through to your device, and then back out through the neutral slot, with the ground slot which offers mainly safety by making sure no excess charges reach you.  

Since many appliances are made of metal and can shock you if there is too much electrical charge built-up, but most appliances are designed not to do this and also your home’s electrical system is made to be connected to the earth as well, which is where your ground wires sends any excess electrical charges – back into the ground.

240 Volt Outlets

You may have noticed some different looking power outlets around your home, such as one of these larger ones which are used to plug in certain appliances like fridges or washing machines, which require more power to run.

240 volt receptacles

These look very different from your standard 120 volt outlet, but they serve the same purpose, only with 240 volts of power at their disposal.

What About 2-Pronged Plugs?

You may also have seen this type of 2-pronged plug around the house as well…

two pronged plug

You may or may not want to use this type of plug, since it lacks the third prong – the ground.  

Without the ground plug, this increases your chances of getting shocked, because if an excess charge builds up in some cheap toaster and has nowhere else to go, it will possibly shock you if you touch the metal surface.

Of course, these two-pronged plugs are still very common to see and, depending on how safe your devices are, your risk of getting shocked can be quite low.  

Still, we don’t recommend you use a two-pronged plug.

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