Electric charge is measured in coulombs (C), the standard unit quantifying electron flow in circuits and static buildup. One coulomb equals approximately 6.24 × 10¹⁸ electrons.
The coulomb honors Charles-Augustin de Coulomb, whose 1785 work on electrostatic force laid foundations for electromagnetism. A single coulomb represents a massive quantity of electrons-enough to power a 60-watt lightbulb for 833 seconds.
| Unit | Symbol | Common Use |
|---|---|---|
| Coulomb | C | Electric circuits, battery capacity |
| Microcoulomb | µC | Small-scale electronics |
| Millicoulomb | mC | Medical devices, defibrillators |
Charge measurement is critical in electrical engineering, physics research, and medical technology. For instance, lithium-ion batteries rate capacity in milliamp-hours (mAh), indirectly measuring charge storage.
A common misconception equates voltage with charge. Voltage measures electric potential difference, while charge quantifies electron quantity. A 9V battery holds far less charge than a car battery rated at 12V.
Static electricity-like the shock from touching a doorknob-results from charge imbalance. Current flow occurs when electrons move through conductors, measured in amperes (amps), representing coulombs per second.
While charge measures electron quantity, energy measures work capacity. A AA battery may hold less charge than a D cell but deliver higher voltage-thus more energy per charge unit.