Definition
A unit of electrical capacitance equal to one-millionth (10⁻⁶) of a farad. It is the standard unit used to express the capacitance of capacitors found in aircraft electrical and electronic equipment. The microfarad is abbreviated µF (or sometimes mfd in older schematics).
Plain English
A small unit used to measure how much electrical charge a capacitor can hold. One microfarad is one-millionth of a farad. Most capacitors in aircraft systems are rated in microfarads because the farad itself is far too large a unit for practical use.
Context Anchor
Seen in aircraft electrical system descriptions, component ratings, maintenance manuals, and wiring diagrams that include capacitors.
Derivation
From the Greek 'mikros' meaning 'small,' combined with 'farad,' the unit of capacitance named after Michael Faraday. The prefix 'micro-' in scientific use means one-millionth. So a microfarad is literally a 'small farad' — one millionth of the base unit.
Why Pilots Care
Capacitors with the correct microfarad rating prevent arcing in magnetos and reduce radio interference; an incorrect value can cause starting problems or electrical noise.
Analogy
A capacitor is a little like a small temporary holding tank for electricity. The microfarad rating is like the size of that tank.
Intuition Check
Do not read microfarad as a measure of voltage or power. It measures how much electrical charge a capacitor can store at a given voltage.
Example Sentence 1
The capacitor in the magneto was rated at 0.25 microfarads.
Example Sentence 2
During an avionics upgrade, the technician selected a filter capacitor with the same microfarad rating as the original part.