Capacitance
Charge stored per unit voltage.
Formula
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How it works
Capacitance tells you how much electric charge a component can hold for each volt across it. The equation C = Q / V comes from comparing the stored charge Q to the potential difference V that causes that charge to be separated and held on the plates or terminals. A larger capacitance means the device can store more charge for the same voltage, while a larger voltage is needed to store a given amount of charge in a small-capacitance device.
When to use it
Use this formula when you know the charge on a capacitor and the voltage across it, and you want to find its capacitance. It is also useful in circuit problems involving energy storage, timing circuits, and any situation where you need to relate charge buildup to voltage.
Worked example, step by step
A capacitor stores 0.006 C of charge when the voltage across it is 12 V. Use C = Q / V. Substitute the values: C = 0.006 / 12. Calculate: C = 0.0005 F. So the capacitance is 5.0 × 10^-4 F, or 500 μF.
Common mistakes to avoid
- Using volts instead of coulombs for Q
- Forgetting that capacitance is charge divided by voltage, not multiplied by voltage
- Not converting units correctly, especially microcoulombs, millifarads, or microfarads
Did You Know?
A one-farad capacitor is enormous; most electronics use micro- or picofarads, millionths and trillionths of one.
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