What is the measuring unit for electric capacitance?

• A. Joule
• B. Henry
• C. Farad
• D. Coulomb

Answer: (C)

Capacitance is the ability of a device to store charge per unit of voltage across its terminals, described by the relation Q = C V. Since the stored charge Q is measured in coulombs and the voltage V in volts, the unit for capacitance must be coulombs per volt. That derived unit is the farad. In other words, 1 farad means 1 coulomb of charge stored per 1 volt of potential difference.

In practical terms, capacitances are often much smaller, so you’ll see microfarads, nanofarads, or picofarads used commonly. For example, storing 2 C at 1 V corresponds to 2 F, while storing 2 C at 2 V corresponds to 1 F.

The other quantities don’t measure capacitance: joule is energy, coulomb is charge, and the henry is the unit of inductance.