What is the unit of electrical current?

• A. Coulomb
• B. Ampere
• C. Volt
• D. Ohm

Answer: (B)

Electrical current is the rate at which electric charge flows through a conductor. The unit for this rate is the ampere, defined as one coulomb passing a point each second. So if one coulomb moves past a point every second, the current is 1 ampere. For example, six coulombs moving past in two seconds equals three amperes. The ampere is distinct from other common electrical units: a coulomb measures amount of charge, a volt measures electric potential difference, and an ohm measures resistance. Current is related to voltage and resistance by I = V / R, and in practice you measure it with an ammeter placed in series in a circuit.