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What are Volts, Amps and Watts?

Need your electricity terminology explained simply? Learn what Volts, Amps, and Watts really are and why they matter.

So when you get your home energy bill, it lists the usage in kilowatt-hours. But when you go to the store, you’ll see things like 12 watts, light bulbs, 9-volt batteries, and vacuum cleaners with 15 amps of sucking power. But what do these numbers even mean? I mean, why do we have so many different units to measure something that seems as straightforward as electricity? Surprisingly, the answer isn’t just so appliance companies and physics professors can confuse you. It’s because several important things have to happen in an electrical circuit for electricity to flow and for work to be done. You can think of a circuit, kind of like the faucet on your kitchen sink. If you want the water to come out, you need two things. You need the water itself and some pressure to force it through the pipes, out your faucet, and into your neti pot.

Similarly, an electrical circuit uses electrons to carry the electricity, kind of like the water in our faucet analogy, but those electrons need something to push them along a circuit. This electrical pressure is what we call voltage and is often provided by two terminals, one with a positive charge and one with a negative charge. So on a battery electrons flow from the negative end through whatever it is you’re trying to power. And then into the positive end where they’ll stay, unless your battery is rechargeable. If you’re plugging something into the wall, this voltage is instead provided by your power company. And although voltage just measures how strongly electricity is being pushed through a circuit, it’s important because many circuits are designed only to accept a certain number of volts, which is why the hairdryer you bought in Monaco might release magic blue smoke if you plug it in, in New York.

What is amps or amperes?

So now that you know what volts are, what about amps? Well, in this context, amp, isn’t short for an amplifier, but rather for ampere, which is a unit of how much electrical charge is flowing past a given point in one second. So when you put volts and amps together, you can tell how much current is flowing and how hard it’s flowing, multiply these numbers. And you get finally our third unit, the wat. Let’s go back to our water analogy for a second and let’s suppose you wanted to spin a small water wheel because you just like watching things spin, or I don’t know, maybe you have it hooked up to an electric motor. Let’s say you have a really powerful water pistol that forces water through a nozzle. Even though the nozzle means the total volume of water flowing per second, isn’t all that much. You wouldn’t want to fill your swimming pool with it.

What is Watts?

The high pressure creates a strong jet that can spin the wheel easily. But suppose instead of a water gun, you have a much wider hose that doesn’t push the water out nearly as strong, but because the hose is a lot wider, more water flows per second overall, and the wheel ends up spinning at the same speed it did with your water gun. If we think of the hose and the water gun pushing out electricity, instead of water, we could say that they’re delivering the same number of Watts for a more practical example. Let’s say you have an 1100 watt power supply for your computer. That’s drawing the full load, so if you plug that into a standard 110 volt, North American outlet, some simple math tells you that 10 amps of current are running through your power supply.

But if you take that same power supply and use it with a 220-volt European outlet, you’re only drawing five amps. But since the amount of power in Watts is the same, your computer will work just fine in both places, even though you’re using different volts and amps. The same thing applies to electric vehicles. As long as you have the same power in Watts, it doesn’t matter if you use a supercharger in Europe or America, even though there are two different standards. Well, that makes sense, but why the heck then is my energy bill in kilowatt-hours? Is that a unit of time? No, actually scientists are just mean it’s a unit of energy Watts and kilowatts express how much energy is consumed per chunk of time. Something scientists call power, which is not the same as energy. But if you multiply kilowatt by an hour, the units cancel and you’re left with a number that shows how much energy that you hogged by running your air conditioner, charging station, and novelty lava lamp all at once.

But what if you’re more concerned about battery capacity instead of what’s coming out of your walls? Well, if you’re buying a replacement battery or a battery pack, you might see their capacity listed in milliamp hours. Again, not time doing the math shows that this is a unit of charge, not energy or power. So going back to our water example, this is like how much water you have in a bucket, not how much is flowing or how fast is flowing. So a bigger bucket means you could charge your phone or car more times.

Author: Morten Pradsgaard

Morten has been working with technology, IoT, and electronics for over a decade. His passion for technology is reflected in this blog to give you relevant and correct information.