Factors Affecting Capacitance

Like a miniature rechargeable battery, a capacitor is a component that can store energy in an electrical charge. It produces a (static voltage) potential difference between its plates. Capacitors come in various shapes and sizes, ranging from bead-like capacitors used in resonance circuits to enormous power or energy factor correction capacitors. They all accomplish that same thing: retain the charge.

A capacitor, in its basic form, a capacitor is built of two or more parallel metallic conductive plates. These plates are slightly separated by air or any insulating material like lightly greased paper, plastic, mica, ceramic, or liquid gel (used in electrolytic capacitors). Dielectric is an insulating layer present between the plates of a capacitor.

What is Capacitance?

Capacitance is a property of an electric conductor or a group of conductors. It is determined by the number of separated electric charges per unit change of electrical potential. Capacitance involves storing electrical energy as well. 

When an electric charge is passed between two originally inert wires, both become evenly charged. One becomes positively changed while the other becomes negatively charged. As a result, a potential difference develops between them. 

Capacitance is denoted by the letter ‘C’. It is defined as the ratio of the charge amount (q) on either conductor to the potential difference (V) between them.

The capacitance is determined by the geometry of the design (e.g., the size of the plates and the spacing between them) and the permeability of the dielectric material between the capacitor’s plates. The permittivity, and consequently the capacitance of dielectric materials, is not dependent on the total charge and the potential difference between conductors.

In general, capacitance is inversely proportional to the distance between the parallel plates of a capacitor, and directly proportional to the size of the plates. It increases as the permittivity of the dielectric material increases.

Formula for Capacitance

The capacitance is a function of the conductors’ physical geometry and the dielectric’s permittivity. Certain factors affect the capacitance of a conductor. 

By altering the physical elements controlling capacitance, a capacitor can be made flexible. The plate area or the extent of plate overlap can be varied in the capacitor’s design.

C = ɛAd

In the given formula,

C = capacitance in Farads,

ɛ = permittivity of a Dielectric,

A = area of a plate overlap in square metres, and

d = the distance between plates in metres.

Depending on the application, the capacitance of each capacitor may be constant or variable. According to the equation, ‘C’ is affected by charge and voltage. In reality, it is determined by the form and size of the capacitor and the insulator used between its plates.

Measurement of Capacitance

A capacitance metre is a piece of electrical test equipment used to measure capacitance, most often of discrete capacitors. The capacitor must be unplugged from the circuit while testing its capacitance.

Capacitance is described as the quantity of electric charge stored inside a conductor. The unit of capacitance is Farad. In other terms, capacitance may be defined as a capacitor’s ability to hold a charge. The higher the capacitance value, the more charge a capacitor can hold.

Factors Affecting Capacitance

Three important variables influence the capacitance of a conductor. These factors can vary the electric field flux and the relative difference of electrons between the plates. They develop for a given amount of electric field force, which is the voltage between the plates.

1. The first factor is the size of the conductor. Greater plate area equals higher capacitance, and smaller plate area equals lower capacitance.
2. The magnitude of separation between the plates is the second factor. When all other parameters are fixed, an increase in plate separation results in decreased capacitance, and vice versa.
3. More dielectric permittivity results in higher capacitance, whereas a lower dielectric permittivity results in lower capacitance.
4. The dielectric is the space between the two parallel plates of a capacitor. It also relies on the conductor’s size. For example, the larger the conductor, the greater is the capacitance value. 

Conclusion

In Physics, capacitance is an important topic. This module helps you understand the basics of this topic. It explains the concept of capacitor and capacitance, the formula for capacitance, measuring capacitance and the factors affecting capacitance.