The Ability to Store Charge
Capacitance ($C$) is the measure of a component's ability to store an electrical charge ($Q$) per unit of potential difference (Voltage, $V$). A capacitor acts like a tiny rechargeable battery that can charge and discharge almost instantaneously.
The standard unit of capacitance is the Farad (F), named after Michael Faraday. However, one Farad is an enormous amount of capacitance; most real-world capacitors are measured in microfarads ($\mu\text{F}$), nanofarads ($\text{nF}$), or picofarads ($\text{pF}$).
The Three Factors of Capacitance
The physical capacitance of a device is determined by:
- Surface Area ($A$): Larger plates can hold more charge.
- Distance ($d$): Plates closer together have a stronger electric field, increasing capacitance.
- Dielectric ($\epsilon$): The insulating material between the plates. Higher permittivity materials increase the storage capacity.
The Formula
Where:
C=
Capacitance (Farads, F)Q=
Electric Charge (Coulombs, C)V=
Voltage (Volts, V)Example Calculation
A capacitor is charged to $12 , \text{Volts}$ and holds a total charge of $0.0012 , \text{Coulombs}$ ($1.2 , \text{mC}$).
- Divide Charge by Voltage: $0.0012 / 12 = 0.0001 , \text{F}$.
The capacitance is $100 , \mu\text{F}$.