What Are Amps, Watts, Volts and Ohms?

what is the amp?

Amperage is another way to measure the amount of electricity running through a circuit. Amperage is the "rate" that current is flowing through the circuit or the number of electrons moving through the wire. Amperage is listed in units called amps (or amperes). The unit is named after French physicist André-Marie Ampère, one of the fathers of electromagnetism.

You might come across amps if you look inside your home's service panel (also called the breaker box). You'll see different circuit breakers listed as 15 amps, 20 amps and 30 amps. The larger the amperage, the more electricity can flow through the circuit. Again, large appliances like air conditioners, washers and dryers will be connected to 30-amp circuits, while most outlets in a home will be powered by 20-amp or 15-amp circuits.

If you try to run too many appliances on the same circuit, the breaker will "trip" and cut off power in order to protect the wiring from overheating.

It is important to understand that metals, such as copper, have electrons that can freely move throughout the material, even at room temperatures. When these electrons move from atom to atom, they displace other electrons already present, resulting in a chain reaction. This property makes metals excellent conductors. In a single copper wire, there are billions upon billions of electrons. To measure the flow of electric current, amps are utilized. One amp, or ampere, is equivalent to one coulomb per second. The coulomb is the unit of electric charge, which is carried by approximately 6.24 x 10^18 electrons. Therefore, a single amp represents 6.24 quintillion electrons passing through a specific point every second. Double that number of electrons flowing per second equates to 2 amps, while half that number is represented by 0.5 amps or 500 milliamperes. To provide some context, the electric current required by the adapter of a typical laptop is 1 amp. In contrast, the current in a lightning strike can range from 5000 to 50,000 amperes, depending on the strength of the storm. For more information on amps, voltage, watts, resistance, and other fundamental concepts, refer to the Electricity videos playlist.

What Is a Watt?

Of all these different units of electricity, wattage is probably the most familiar. For years, you've been buying 40-watt light bulbs and 60-watt light bulbs with the general understanding that a 60-watt bulb is going to be brighter than a 40-watt bulb. But why?

Wattage, it turns out, is the amount of power an electric device consumes. Another way to think about wattage is "electricity at work" — the power it takes to actually do something, whether it's running a vacuum (400 to 900 watts), ringing the doorbell (2 to 4 watts) or illuminating a light bulb (40 to 75 watts).

To calculate wattage, you simply multiply voltage (pressure/speed) by amperage (volume), expressed as V x A = W. The faster each electron moves through the circuit, and the greater the volume that the circuit can hold, the higher the wattage. Wattage is measured in units called watts and named after James Watt, the Scottish engineer who popularized the steam engine.

What Are Ohms?

Ah, you thought we were done. So far, we've talked about different ways to measure the amount of electricity flowing through a circuit, and how much wattage is needed to run different electrical devices connected to that circuit.

But circuits are made up of wires and wires are not perfect conductors. Most home electrical wiring is made of copper or aluminum, and both of those materials have a certain amount of natural resistance or friction, which slows down the flow of electricity. When electricity passes through electrical devices and appliances, they also apply their own resistance.

Resistance is measured in ohms, which are named after the German physicist and mathematician Georg Simon Ohm.

If you're still a little confused about the relationship between volts, amps, watts and ohms, keep reading for a helpful analogy.

Understanding Electricity: The Plumbing Analogy

A neat analogy to help understand these terms is a system of plumbing pipes. The voltage is equivalent to the water pressure, the current (amperage) is equivalent to the flow rate, and the resistance is like the pipe size.

There is a basic equation in electrical engineering that states how the three terms relate. It says that the current is equal to the voltage divided by the resistance or I = V/R. This is known as Ohm's law (named after our friend Georg Simon Ohm).

Let's see how this relation applies to the plumbing system. Let's say you have a tank of pressurized water connected to a hose that you are using to water the garden.

What happens if you increase the pressure in the tank? You probably can guess that this makes more water come out of the hose. The same is true of an electrical system: Increasing the voltage will make more current flow.

Let's say you increase the diameter of the hose and all of the fittings to the tank. You probably guessed that this also makes more water come out of the hose. This is like decreasing the resistance in an electrical system, which increases the current flow.

Electrical power is measured in watts. In an electrical system power (P) is equal to the voltage multiplied by the current.

The water analogy still applies. Take a hose and point it at a waterwheel like the ones that were used to turn grinding stones in watermills. You can increase the power generated by the waterwheel in two ways. If you increase the pressure of the water coming out of the hose, it hits the waterwheel with a lot more force and the wheel turns faster, generating more power. If you increase the flow rate, the waterwheel turns faster because of the weight of the extra water hitting it.