Electric Current
Electricity and Magnetism

Why I?

Stories from Physics for 11-14 14-16 IOP RESOURCES

The use of the symbol “I” for current might seem counterintuitive but the label arises from a historical French term. In the 1820s, André-Marie Ampère showed that two parallel, current-carrying wires will attract or repel each other depending on the direction of the currents flowing through them. From this observation, he developed the eponymous Ampère’s law, which relates the size of the force between two conductors to the length of the wires and the magnitude of the current. He labelled the flow of charge “intensité de courant”, meaning current intensity, and gave it the symbol “I”.

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