ampere

The ampere or amp (Symbol: A) is the standard unit of electric current. For instance, 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.

Other websites

• The NIST Reference on Constants, Units, and Uncertainty
• A short history of the SI units in electricity