Which quantity is measured in amperes (A)?

• A. Length
• B. Time
• C. Electric current
• D. Luminous intensity

Answer: (C)

The main idea is understanding what each unit tells you about a physical quantity. An ampere measures electric current, which is the rate at which electric charge flows through a conductor. In other words, it tells you how much charge passes a point each second. The relationship is I = ΔQ/Δt, so if 1 coulomb of charge moves past a point every second, the current is 1 ampere.

This differs from the other quantities listed. Length is measured in meters, which describes how long something is. Time is measured in seconds, which describes how long something lasts. Luminous intensity is measured in candelas, describing how bright a light source is. None of these describe the flow of electric charge, which is what amperes quantify.

So, the quantity measured in amperes is electric current—the rate at which electric charges move through a circuit. For example, if 2 coulombs pass a point each second, the current is 2 amperes.