Jargon busted – Amps

The electrical world can be confusing and we’ve all come across some terms that don’t make much sense. That’s why in each issue of Wired we unravel a piece of industry gobbledygook and tell you what it means – In plain old English.

What is an amp?
An amp – or ampere, to give it its full name –  is an electrical unit used to measure current (or electron flow) in an electrical conductor. It’s equal to a flow of one coulomb per second.

One amp in an electrical circuit is the amount of current that is produced by a force of one volt (named after Volta) acting through the resistance of one ohm (see our Bright Spark feature on Georg Ohm).

It’s also an anagram of ‘map’ and ‘Pam’ – although this, of course, has nothing to do with electric circuits.

Where does the name come from?
The amp is named after André-Marie Ampère (1775-1836). You can probably guess by his name that he was French; born in Lyon – he was also a renowned physicist and mathematician, who worked in the field of what he called electrodynamics, now more commonly called electromagnetism.

How did Ampère come up with the idea?
Ampère was interested in the relationship between electricity and magnetism and spent time working on mathematical and physical theories to support his ideas.

Through experimentation, he found that when the direction of the current carried by two parallel wires was altered, it affected whether they attracted or repelled each other.

What is Ampère’s Law and why is it important?
This states that the mutual action of two lengths of wire carrying a current is proportional to their length and the intensity of the current flowing through them. Ampère’s Law is one of the foundations of electrodynamics – indeed Ampère is often considered the “father of electrodynamics”.

When was the amp so named?
In 1881, an international convention established the ampere or amp as a standard unit of electrical measurement, alongside the volt, ohm, coulomb and watt.

What has this got to do with the Eiffel Tower?

When Gustave Eiffel built his eponymous tower, completed in 1899, he engraved the names of 72 scientists on the borders of each of the four sides of the Paris landmark – and one of the names was Ampère. These were painted over during one early repaint, then restored over the course of 1986-87.