Definition
The standard unit of electrical charge, equal to the quantity of charge transferred by a current of one ampere flowing for one second. One coulomb represents approximately 6.28 × 10^18 electrons.
Plain English
A coulomb is a way of measuring how much electricity has moved past a point. If one amp of current flows for one second, one coulomb of charge has gone by.
Context Anchor
Seen in aircraft electrical theory, especially when discussing current, charge, batteries, and circuit behavior.
Derivation
Named after Charles-Augustin de Coulomb, an 18th-century French physicist who studied electrical forces. Knowing the unit is named after a person explains why it does not break down into simpler word parts.
Why Pilots Care
Battery capacity, current flow, and electrical load calculations all rest on this basic unit. Understanding the coulomb makes amps, amp-hours, and battery ratings make sense rather than feeling like arbitrary numbers.
Analogy
Think of current (amps) as the flow rate of water through a pipe, and a coulomb as a fixed bucket-sized amount of that water. One amp flowing for one second fills one bucket.
Intuition Check
Do not confuse coulomb with ampere. Coulombs measure an amount of electric charge; amperes measure how quickly that charge is moving.
Example Sentence 1
One amp of current flowing for one second moves one coulomb of charge through the circuit.
Example Sentence 2
The battery released a measured number of coulombs to power the starter motor.