electrical plugs

Why Do Electrical Plugs Have Holes?

While electrical plugs are a part of our everyday existence, many of us don’t understand exactly how they work. Did you know electrical plugs are responsible for over 34,000 household fires every year? Understanding what electrical plugs do and the purpose of electric plug holes can prevent injury and death.

But, there are more cool things to learn about electric plug holes. If you’re looking to break into the automation market, starting your knowledge from the basics is a great strategy. Knowing exactly the purpose of electrical outlets and how they operate is essential for success in an electrical hobby or career.

Continue reading to learn everything you need to know about how electrical outlets work and what ones are common in North America.

The Basics: How Does Electricity Work

Knowing how a home or office outlet works requires understanding the basics of electricity. The movement of an electrical current requires a metal conductor. This is the wiring in the wall and the switch within the building’s electrical system.

Electricity travels in a loop. It powers the electrical outlet from a source, such as a city grid or a fuel-powered generator. In a home or office, it reaches the service panel where it is distributed through a circuit.

This circuit makes energy available to connected endpoints. These include appliances directly connected like a hot water heater or a heat pump. The circuit also provides energy to wall outlets for plugin appliances.

How Do Electrical Plugs Work?

Electrical outlets, sometimes called electrical sockets or wall plugs, let appliances connect to the electricity grid. This grid gives an alternating current to the source outlet. Alternating currents make use of transformers for efficiency.

The holes in the outlet are commonly called sockets. And, the reason electrical plugs have more than one hole is that the energy flows through them. Both sides of the outlet are considered terminals for the energy to transfer through.

The metal wiring for electrical plugs must have a hot wire and a neutral wire. The hot wire transfers the energy from the service panel into the outlet. The neutral wire transfers unused electricity back to the panel.

North American outlets usually provide 120 volts of power. Other places around the world have different voltages. The size of the socket and its shape may also vary, but this doesn’t affect how the outlet works.

Purpose of Electric Plug Holes

Both sides of the outlet are essential for the transfer of energy to work. There is the visible side, usually covered with a wall plate. The other side of the outlet has the wiring that brings the energy from the circuit.

The holes, or slots, in the electrical plugs allow the flow of electricity into the appliance. An electric current runs from the hot slot and back through the neutral slot. Electrical cords with three prongs are connected to the building’s grounding system.

The prongs of an electrical cord are made of metal to conduct the energy transfer from the outlet. Some cords and outlets have two prongs and others have three. The third prong is a way to ensure safety on appliances that have a metal casing.

All approved outlets are polarized, meaning the holes are different sizes. Here are the two common outlets found in most homes and offices:

North American Type A Outlets

Type A outlets have two holes, or slots, for the prongs to enter. These prongs are flat and one is larger than the other. The larger prong connects to the neutral slot, while the smaller prong connects to the hot line.

The two metal prongs complete the electric current loop from the hot slot to the neutral slot. These slots connect to the metal wires attached to the other side of the outlet. Two prong outlets are known as polarized nonground-type outlets.

Nowadays, these two-hole receptacles are uncommon. Since the 1960s, all buildings in the United States are required to have grounded outlets installed. A grounded outlet has a third hole that connects to a grounding wire.

While two-prong cords are still common on appliances without metal casing, the outlets they go into usually have three holes to accommodate grounded plugs. Two-prong plugs are not unsafe for appliances without metal casing.

North American Type B Outlets

Type B outlets come with three holes. These include the two flat slots for the hot and neutral prongs and also a round or curved pin. This pin, called the earth pin because the wiring goes to a ‘dead’ end, acts as the grounder for the outlet.

It is longer than the flat prongs for a safety measure. Because the grounding pin is longer, it is the first to connect within the outlet. This ensures the hot wire doesn’t get inserted first.

The earth pin acts as a safety measure for short circuits. But, these plugs still pose a danger for electric shock. Even if the prongs are only halfway in the socket, the electricity transfer still occurs.

What Do the Holes in Electrical Prongs Do?

You may have noticed that the prongs on your electrical cords have one or two circular holes at the end of them. These holes serve an important purpose as a safety measure. Inside the slots, most outlets have raised ridges or bumps.

These bumps fit inside the holes at the end of the prongs. This creates a stronger grip within the outlet and prevents the prongs from sliding out accidentally. The firmer grip on the prongs creates a more stable contact for the flow of energy.

Manufacturers use the holes at the end of the cord prongs to attach safety information. A zip-tied message is often found through these holes that requires cutting away before use.

Some outlets do not have the raised ridges inside the slots at all. Instead, they use blades to grip the prongs.

Improved Safety Electrical Outlets

Thankfully, technology has advanced to provide more safety measures against electrocution. While old outlets still exist without grounding pins, spring-action blades, or raised ridges for security, most get removed from service. Safety outlets such as ground-fault circuit interrupters and tamper-resistant outlets save lives every year.

Tamper-Resistant Electrical Plugs

These outlets have spring-loaded shutters that activate to close over the flat slots in the outlet. The flat slots remain blocked until the longer, earth pin gets inserted. This activates the spring to pull the shutters back and allow the prongs into both the hot slot and neutral slot at the same time.

These types of outlets are particularly helpful for those with young children. They prevent accidental electrocution from the metal getting inserted into the hot wire slot.

Ground-Fault Circuit Interrupter Electrical Plugs

Ground-fault circuit interrupter (GFCI) outlets are commonly found in bathrooms and kitchens. These wall outlets protect against electrocution where water may enter the outlet. GFCI outlets have an internal monitor that detects a surge in electrical use.

Where a fuse in a building’s service panel gets overloaded, it shuts down the electricity to the outlet. A ground-fault circuit interrupter outlet stops the flow of power inside the unit. It monitors the amount of electricity flowing through the outlet and cuts power if an interruption is detected.

An interruption of flow is when the electricity isn’t flowing from hot to neutral. If an imbalance of flow is detected, the monitor shuts down the circuit inside the outlet.

Getting an electric shock is called a ground fault. Moisture is one of the leading causes of ground faults for people. GFCI outlets help prevent this from occurring because it stops the flow of electricity through you and into the ground.

GFCI outlets include one or two buttons and often an indicator light built into them. The test and reset buttons are important safety features because the interrupter circuit does wear out eventually.

Pressing the test button trips the circuit and stops the flow of electricity from the outlet. Pressing the reset button turns it back on. It’s important to test these at least once a month to ensure the interrupter circuit is functional.

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