Diagram of the definition of the ampere

The ampere or amp (Symbol: A) is the standard unit of electric current. An electric current of one amp is one coulomb per second. The amp is named after André-Marie Ampère who studied electromagnetism.

The amp is defined using two parallel wires placed one metre apart in a vacuum. The wires are very long and very thin. One amp is defined as the current producing an attractive force of 2×10–7 newtons per metre of length between these wires.[1]


  1. Paul M. S. Monk, Physical Chemistry: Understanding our Chemical World, John Wiley and Sons, 2004 online.

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