What Are Capacitance and Inductance?
Capacitance and inductance are the energy-storage properties of components. Capacitance stores charge in an electric field, inductance stores energy in a magnetic field. (This article covers the property; for the parts themselves, see the capacitor/coil categories.)
What Is Capacitance?
Capacitance is a component's ability to store electric charge; its unit is the farad (F). A capacitor accumulates charge when voltage is applied and releases it when the voltage is removed.
What Is Inductance?
Inductance is a component's ability to store energy in a magnetic field; its unit is the henry (H). When current flows through a coil, a magnetic field forms around it and opposes sudden changes in the current.
Comparison
| Property | Capacitance | Inductance |
|---|---|---|
| Stores | Electric field (charge) | Magnetic field (current) |
| Unit | Farad (F) | Henry (H) |
| Opposes | Change in voltage | Change in current |
AC Behavior (Reactance)
In an AC signal, both show frequency-dependent reactance: as frequency rises, a capacitor's opposition falls while a coil's rises. This opposite behavior is the basis of filter and resonance circuits.
Common Mistakes
- Getting the scale wrong: 1 F is huge; in practice µF/nF/pF and mH/µH are used.
- Confusing the two: capacitance opposes voltage change, inductance opposes current change.
- Forgetting DC behavior: in DC, a capacitor (once charged) blocks current, while a coil behaves like a short circuit.
Frequently Asked Questions
Are capacitance and a capacitor the same?+
Which one stores energy?+
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