Why Is One Prong Bigger On A Power Cord?

4 Minutes Read

Electricity is a pretty magical thing. But, while we use it daily, many people do not understand its science. So, it isn't surprising that a common question about electricity is why one of the prongs on a power cord is always bigger than the other.


We're here to answer this question and demystify this for you.


The reason why one prong is bigger than the other has to do with the way electricity flows.


Electricity is the electron flow or the tiny particles that flow around a circuit. For the electrons to flow, there needs to be a complete circuit - meaning that there needs to be a path from the negative terminal to the positive terminal.


If there is a break in the circuit, the electrons can't complete the circuit, and the power won't work.


The two prongs on a power cord are different because they provide this path for the electrons to flow in different ways. The larger prong is called the "hot" prong and carries the electricity to the appliance. The hot prong remains connected to the live wire.


The smaller prong, called the "neutral" prong, returns the electricity to the source. The neutral prong connects with the neutral wire.


When plugged in, the electricity creates a circuit that flows from the hot prong to the appliance and back through the neutral prong.


The different sizes of the two prongs help to ensure that the electricity can flow in the right direction and that there is less chance of an electrical shock.


Now that you know why one prong is bigger on a power cord, you can rest assured that your appliances are getting the power they need in the safest way possible.


What Does UL Listing Have To Do With Electrical Prongs?


You may have noticed that some electrical devices have a "UL" logo. UL is short for Underwriters Laboratories, a globally recognized leader in product safety testing.


An electrical device must meet specific safety standards to bear the UL logo. These standards protect users from electrical shock and fire hazards.


One of the safety standards that a device must meet is having the correct size and type of prongs for the voltage the device rating. Doing so helps to ensure that the current flowing through the device is not too high, which could cause a fire hazard.


So, when you see a UL logo on an electrical device, you can be confident that it meets necessary safety standards.


What Are The Dangers Of Non-UL Listed Devices?


Non-UL listed electrical appliances may not have been safety tested at all, or they may not have met all of the safety standards required for UL listing.


Unlisted instruments create a greater risk of causing an electrical shock or fire. Non-UL Listed devices that could be problematic could include power strips, surge protectors, and extension cords. Other items, such as craft lamps, may have a UL Listing, but only for specific voltages.


If you are using any Non-UL Listed electrical devices, it is essential to be extra careful. Use them only for low-power devices such as lamps and chargers. Please do not use them for high-powered appliances such as hair dryers, toaster ovens, or space heaters.


Ensure regular inspections to look for signs of damage, and avoid using them if they are damaged. If you have doubts about their safety, it is best to replace them with UL Listed devices.


Why Do Some Power Cords Have A Ground Wire?


Some power cords also have a third wire, called a ground wire. The ground wire provides an extra path for the electricity to flow in case there is a break in the circuit.


Grounding protects users from electrical shocks. The ground wire connects to the ground prong, which is usually the longest.


If you see a power cord with a ground wire, it is essential to use it only with outlets with a ground slot. The ground wire will not be effective if you use an outlet with no ground slot.


How To Tell If An Outlet Has A Ground Wire?


If you are unsure whether or not an outlet has a ground wire, there are a few ways to check. First, look at the outlet. If there are three slots, one of them should be slightly larger than the other two. The longer one is the ground slot.


If you do not see a ground slot, the next step is to check the wiring. First, remove the cover plate from the outlet and look at the wires. If a green or bare copper wire connects to the grounding screw, the outlet has a ground wire.


If unsure, you can use a circuit tester to check for a ground wire. With the power off, insert the circuit tester into each slot. If the light on the circuit tester comes on, then there is a ground wire.


Why Do Some Outlets Have Two Hot Wires And No Ground Wire?


In some cases, outlets have two hot wires and no ground wire. These types of outlets are called ungrounded outlets. They are less safe than grounded outlets because there is no ground wire to provide a different path for electricity in case of a break in the circuit.


Fortunately, the likelihood of having ungrounded outlets is low in the modern day. Most new homes have standard grounded outlets. In addition, most older homes have undergone electrical upgrades to add grounding wires and electrical capacity to handle the demands of today's technology.


If you have an ungrounded outlet, the best course of action is to have it replaced by a qualified electrician. In the meantime, be extra careful when using this outlet device. Only use low-powered devices, and do not use them if they are damaged.


So, now you know the answer to one of life's great mysteries - why is one prong on an electrical cord longer than the other? 


Hopefully, you've also gained a greater understanding of the importance of electrical safety and grounding. If you have questions about the wiring in your home or business in the Tri-State area, please call Premiere Electric Company for help. They can help you stay safe in a potentially dangerous situation.

Still Have Questions? Talk To An Electrician.

Picture of Tom Baynum

Tom Baynum

Tom is the owner of Premiere Electric. He is a Master Electrician and started in the electrical field in 1987 and started his own business January 1990. His hobbies include coaching girls fastpitch softball for the last 27 years and coaching at Bishop Brossart High School since 2004. He has 4 grand kids now and loves helping them in sports & watching them compete.