Fact Checked

What is the Ampere?

Daniel Liden
Daniel Liden

The ampere, often referred to as the amp, is a unit of measurement for electric current. The term "electric current," often symbolized by the letter "I" in calculations involving current, refers to the rate of flow of electrical current, or the amount of electrical charge that passes a given point in a circuit in a certain amount of time. One ampere is equivalent to one coulomb per second, and one coulomb is equal to 6.24 x 1018 electrons, so one ampere is equivalent to 6.24 x 1018 electrons passing a given point in a circuit in one second. Coulombs and amperes are closely related in that the former represents the amount of charge running through a circuit while the latter represents the rate at which that charge flows.

The "ampere" is named after André-Marie Ampère, a French physicist and mathematician who conducted significant research in the area of electromagnetism. It belongs to the Système International d'Unités, or SI unit system, which is the standard international system of units used in science. This system of units is useful because most people working in science are familiar with them and because they tend to be fairly easy to understand and to convert when necessary.

A multimeter, a device that can be used to measure amperage.
A multimeter, a device that can be used to measure amperage.

Many other units of measurement with more specific purposes in science and industry make use of the ampere as a base unit. The ampere hour, for instance, is equal to 3600 coulombs, or the amount of charge built up from a steady one amp current running for one hour. This unit is often used to describe the charge capacity of batteries.

Electrical current is closely related to the ideas of electrical resistance, measured in ohms, and electrical conductance, measured in siemens. Resistance is a measure of how strongly a material impedes the flow of electrical current while conductance, conversely, describes how easily a current can flow through a material. In many cases, the current that can flow through a given material varies based on the temperature of the material.

An ammeter is a device that measures, in amperes, the flow of electrical current through a material. Different types of ammeters are made with different levels of sensitivity in order to accurately measure currents much higher or lower than one ampere. Ammeters have a variety of both scientific and commercial applications. They can be used in experiments concerning electricity and magnetism, as energy meters for power companies, or to estimate the amount of charge contained in batteries.

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Discussion Comments


The ampere has never been defined in terms of the rate of flow of electrical charge. It's defined in terms of the force between two, parallel, current-carrying conductors. Before this definition, it was defined into the amount of silver deposited on an electrode during electrolysis over a specified period of time.


@irontoenail - I hope that you do understand as thoroughly as possible the way electricity works. And also the many ways it can go wrong. I always worry when I hear about people teaching themselves how to make electrical gadgets online, because it can be dangerous. Especially if you are working with too many amps.

It is always a good idea to learn the rules when working with electricity, and obey them. You don't have to understand them all the time. This is especially true of people with heart conditions as even less than one ampere unit can mess with the heart in an electric shock.

I don't want to put anyone off working with electricity. Just be careful and make sure that the people around you are going to be safe as well.


@croydon - Well, looking up basic electrical terms online, like this article, is a good start. You can still educate yourself on how electricity works.

I find they don't quite go deep enough at high school for me to really "get" it. It was only when I started doing my own research that more of it clicked into place.

Like for example the fact that the definition of an ampere is a certain amount of electrons passing a given point in a second. Stuff like that makes it much easier for me to imagine and extrapolate what is happening in my little projects.


I remember when we studied electricity in high school, I was completely turned off the idea, which I now think is a shame.

We were given little electric sets and told to make the light bulb glow by connecting various bits and pieces. Or sometimes we had to make a beeper work.

And then we had to write up about the number of amps and so forth. I think we even used an ammeter.

But I could never get the things to work. It never quite clicked with me.

Now I have some friends who fuss around with LED lights and things, and make some awesome little creations and I feel left out.

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    • A multimeter, a device that can be used to measure amperage.
      By: pokchu
      A multimeter, a device that can be used to measure amperage.