Question 1

What is capacitance?

Accepted Answer

Capacitance is the ability of a component to store electrical energy in an electric field. It is defined as C = Q/V, the ratio of charge stored (Q) to the voltage across the capacitor (V). The SI unit is the Farad (F), but practical capacitors are typically measured in microfarads (μF), nanofarads (nF), or picofarads (pF).

Question 2

How much energy does a capacitor store?

Accepted Answer

The energy stored in a capacitor is E = ½CV², where C is the capacitance and V is the voltage. This energy is stored in the electric field between the plates. Doubling the voltage quadruples the stored energy, which is why high-voltage capacitors can be dangerous.

Question 3

What determines a capacitor's capacitance?

Accepted Answer

For a parallel-plate capacitor, C = ε₀εrA/d, where ε₀ is the permittivity of free space, εr is the relative permittivity (dielectric constant) of the material between plates, A is the plate area, and d is the separation between plates. Larger plates, closer spacing, and higher dielectric constant all increase capacitance.

Question 4

Why is a Farad such a large unit?

Accepted Answer

One Farad means storing one Coulomb of charge at one Volt, which requires an enormous capacitor by everyday standards. A 1 F capacitor with parallel plates separated by 1 mm would need plates of roughly 100 km². Most practical capacitors range from picofarads to millifarads, though supercapacitors can reach hundreds of Farads.

Capacitance Calculator (C = Q/V)

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