Ampere (A)

Named after André-Marie Ampère, measuring the volume of electrons flowing past a point per second.

The fundamental SI unit of electric current, the ampere defines the rate of electrical charge flow through a circuit. It forms the backbone of electrical engineering and power distribution calculations. In the early decades of submarine telegraphy, maintaining a consistent current across thousands of miles of undersea cable proved an immense practical challenge, and insulation was frequently melted by engineers working ahead of the physics that would later explain why.