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Capacitor vs Inductor: Key Differences Explained

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This article explores the differences between capacitors and inductors, two fundamental electronic components.

Capacitor

A capacitor is an electronic component designed to store electrical charge. In its simplest form, it consists of two parallel metal plates separated by an insulator, known as a dielectric.

Crucially, a capacitor does not allow direct current (DC) to flow through it, but it does allow alternating current (AC) to pass.

capacitor symbol Figure 1: Various capacitor symbols (fixed, variable, and polarized).

Polarized capacitors require proper connection: current must enter through the positive terminal. Non-polarized capacitors can be connected either way around.

Capacitor Basics

Capacitance is measured in Farads (F), but in practice, you’ll often encounter units like µF (microfarads), nF (nanofarads), and pF (picofarads). Typical capacitance values range from 1pF to around 150,000 µF.

When choosing a capacitor for a specific application, you’ll need to consider its value, tolerance, and stability.

Inductor

In its simplest form, an inductor is a coil of wire, often wound around a core. This core can be air or a magnetic material like iron. An inductor with a magnetic core exhibits a significantly higher inductance compared to an air-cored inductor. The more turns in the coil, the greater the inductance.

Inductors oppose changes in current and possess inductance, denoted by “L”.

Inductor

Inductance is measured in henries (H), millihenries (mH), and microhenries (µH).

Inductor Basics

Difference between Capacitor and Inductor

The following table summarizes the key differences between capacitors and inductors:

FeatureCapacitorInductor
DC CurrentBlocks direct currentPasses direct current
AC CurrentPasses alternating currentBlocks alternating current
Voltage ChangeVoltage cannot change instantlyCurrent cannot change instantly
Rapid Change EffectsQuick voltage change generates large currentQuick current change generates large voltage
Energy StorageStores energy in an electric field (E)Stores energy in a magnetic field (H)
Frequency BehaviorConducts best at high frequenciesConducts best at low frequencies
Unit of MeasurementFaradsHenries
Major TypesCeramic, electrolytic, tantalumMultilayer, ceramic core, coupled
Voltage/Current PhaseVoltage lags behind currentCurrent lags behind voltage
ReactanceCapacitive reactance (XC) = 1/(2πfC)Inductive reactance (XL) = 2πfL
Series Combination(1/C) = (1/C1) + (1/C2) + … + (1/Cn)L = L1 + L2 + … + Ln (Assuming no mutual inductance)
Parallel CombinationC = C1 + C2 + … + Cn(1/L) = (1/L1) + (1/L2) + … + (1/Ln) (Assuming no mutual inductance)