Why Are the Holes in My Outlets Different Sizes?

If you’ve ever looked closely at an electrical outlet, you’ve more than likely noticed that the slots in your outlet are not the same size. When looking at the outlet, the slot on the left is usually the longer one (when the ground pin hole is on the bottom, as usual). Why is this the case? Did someone make a mistake when filing for the patent and now they just have to live with it?

Believe it or not, this is entirely by design—it’s an ultra-important safety feature designed to prevent massive sparks, fires, overheating, and possibly electrical injuries or electrocution.

Different Slots, Different Polarity

Electricity has two different polarities to every circuit: positive and negative. This is why your electrical outlet has two main prongs: one is a positive side and the other negative. When you plug a device in, you need to plug the positive pin into the positive side of your outlet and the negative pin into the negative side for your device to work properly.

But what happens if you plug them in backward? The answer: nothing good. Electricity generally flows from the negative side to the positive side through your circuit. When you reverse the polarity of a circuit, electricity flows through it backward and quickly overloads different components and circuits. This creates a short, allowing a surge of current to flow through the wires and components, resulting in overcurrent, overheating, the potential for huge sparks, and possibly even serious injuries if you aren’t careful. It’s perhaps the single most important rule of handling electricity: positive to positive and negative to negative, and never cross the two.

This is exactly what the different sized slots are designed to prevent. If you look closely at plugs for some devices, you will notice that the prongs themselves are different sizes as well. The larger prong is intended to go in the larger slot, and the smaller prong into the smaller slot. The larger prong is actually too large to fit into the smaller slot, thus preventing you from plugging that device in backward. When you can’t plug the device in backward, you can’t accidentally cross the circuit and create the serious safety hazard we talked about a moment ago.

What About Devices With Two of the Same Size Prong?

If you look at some of your plugs, you may have noticed that the two prongs are actually the same size. This is not a safety hazard; the device you’re holding has components and circuits installed that protect against reversed polarity. To put it simply, most of these devices can accept power from either polarity because the circuits installed can utilize it flowing in any direction. These devices also almost exclusively use DC power, meaning they have an inverter installed that converts the current flowing through your walls to a different type of current that’s more commonly used in small devices. In these cases, it’s perfectly okay to insert your plug in either direction; the device will work as anticipated either way.

What’s That Third Hole in My Plug?

Unless you live in a home with an electrical system that was constructed before the 1950s, there’s a good chance that all of your outlets also have a smaller third hole located beneath and between the two main prongs. This is for your ground prong. Your ground prong is yet another important safety device that allows surges and overloads to have somewhere to flow safely to. If they don’t have anywhere they can go, surges can cause meltdowns, fires, burn injuries, and more. Thus, devices that use larger amounts of voltage or current are required to have these ground pins on their plug as well as ground circuits installed.

Plugs with this ground pin have an extra wire hooked to them that carries this excess of current away safely when needed. Never remove the ground pin from a device that has one in order to get it to plug into a two-prong plug, and likewise, never assume that simply placing a three-prong plug in your walls provides you with proper grounding. Every plug needs to be tapped into a ground circuit in order to be safe, and a professional electrician should be the one to conduct this service.

If you are concerned about an electrical outlet in your home, or you want to improve your electrical safety with modernization and upgrades, call the experts from A-TEMP Heating, Cooling & Electrical at (503) 694-3396 today!