Capacitance is the ability of a component or circuit to collect and store energy in the form of an electrical charge. This energy is stored by the use of an electronic component called capacitor.
Capacitors are energy-storing devices available in many sizes and shapes. The capacitor contains a pair of plates, in which when a steady voltage is applied across a capacitor, a +Q charge is stored in one plate and – Q is stored on the opposite plate. Capacitors and batteries both store energy. While batteries release energy gradually, capacitors discharge it quickly
Capacitance is expressed as the ratio of the electric charge on each conductor to the potential difference between them. The capacitance is proportional to the area of its plates, whereas it is inversely proportional to the distance between the plates.
Capacitance can be increased when:
• A capacitor’s plates (conductors) are positioned closer together.
• Larger plates offer more surface area.
• The dielectric is the best possible insulator for the application.
In electrical circuits, capacitors are frequently used to block direct current (dc) while permitting alternating current (ac) to flow.
The capacitance value of a capacitor is measured in farads (F) units named for English physicist Michael Faraday (1791–1867). The SI unit of capacitance is farad (F), where one farad is equal to one coulomb per volt.
The capacitance, “C”, of a capacitor is defined as the ratio of the magnitude of the charge, Q on either conductor to the potential difference, V between the conductor.
C(farad) = Q(coulomb) / V(volt)
Q – Electrical Charge
V – Potential Difference
1. Determine the capacitance if charge stored on either plate of capacitor is 48 x 10-6 and connected across a 12 Volt battery .
C = Q / V
C = 48 * 10-6 / 12
C = 4 * 10-6 F
Capacitance = 4 * 10-6 Farad
2. Determine the amount of electrical charge if the capacitance is 3 x 10-14 F and voltage across the capacitor is 0.5 V .
C = Q / V
3 * 10-14= Q / (0.5)
Q = 3 * 10-14 * 0.5
Q = 1.5 * 10-14 C
Electrical Charge = 1.5 * 10-14 Coulomb
The standard unit of measurement for capacitance is farad (F), i.e. (C/V)
A capacitance of 1 F produces 1 V of potential difference for an electric charge of one coulomb (1 C)