This article describes the prominent differences between a capacitor and an inductor that set them apart based on several factors.
Capacitor and Inductor are two electrical components used in electrical and electronic circuits. They differ in functionality, current flow, and energy storage capacity, and they have different performances under alternating current(AC) and direct current(DC) flow circuitry.
What is a Capacitor?
A capacitor is defined as a passive electronic device that is responsible for storing electric charge in the electrostatic field. Due to its inability to produce and amplify the electric power and current in the circuit, it is termed a passive element of the circuit. A capacitor is comprised of a pair of parallel metallic plates. The space between the two metallic plates is filled with a dielectric medium, usually air or any other fluid. The capacitor stores the potential energy acquired in the electrostatic field, which is generated by the pair of plates of the capacitor.
The symbolic representation of a capacitor is given below in Figure-1.
The term capacitance in relation to the capacitor is defined as the capacity of the capacitive device to store the potential energy as an electrostatic field. The SI unit of capacitance is Farad (F) The expression to determine the capacitance of the capacitor is given below.
Where C is the capacitance of the capacitor, εr is the relative permittivity of the dielectric medium, ε0 is the permittivity of air, A is the cross-sectional area, and d is the distance between plates of the capacitor.
What is an Inductor?
An inductor is defined as a passive electronic device that is responsible for storing electrical energy in a magnetic field. Due to its inability to produce and amplify the electric power and current in the circuit, like a capacitor, the inductor is also a passive element of the circuit. An inductor is constructed by simply winding a coil of wire.
The symbolic representation of an inductor is given in Figure-2 below.
The term inductance in relation to an inductor is defined as the capacity of the inductive device to store the potential energy as a magnetic field. The SI unit of inductance is Henry (H) The expression to determine the inductance of the inductor is given below.
Where L is the inductance of the inductor, µ is the permeability of the core, N is the number of turns in the inductor coil, l is the mean length of the magnetic core, and A is the area of cross-section.
Difference between Capacitor and Inductor
The table below lists the important differences between a capacitor and an inductor.
| Parameter | Capacitor | Inductor |
| Definition | A capacitor is a passive device that only stores and dissipates electric energy in the electric field. | An inductor is a passive device that only stores and dissipates magnetic energy in the magnetic field. |
| Construction | A capacitor is made up of two metallic plates placed parallel to each other with insulating material between them called the dielectric material. | An inductor is a simple coiled wire. |
| Working principle | The capacitor operates on the basis of the electrostatic mechanism, according to which, the capacitor begins storing electric charge in its electric field when it is charged with voltage. | The inductor functions on the basis of an electromagnetic mechanism, according to which the coil of the inductor generates a magnetic field when current passes through the coil. |
| Active / Passive device | A capacitor is a passive device as it can only store energy in its electrostatic field but cannot produce or generate power or electric current in the circuit. | An inductor is also a passive device as it can only store energy in its magnetic field but cannot produce or generate power or electric current in the circuit. |
| AC and DC power affects | A capacitor has the ability to allow the flow of alternating current (AC), but it prohibits the flow of direct current (DC) through it. | An inductor has the ability to allow the flow of direct current (DC), but it prohibits the flow of alternating current (AC) through it. |
| Types | Capacitors can be of different types such as supercapacitors, hybrid capacitors, mica capacitors, ceramic capacitors, etc. | Inductors can be of different types based on the material of the core namely – air core inductor, iron inductor, ceramic core inductor, steel core conductor, etc. |
| Voltage and current relationship | Voltage lags current by a phase difference of 90 degrees. | Voltage leads current by a phase angle of 90 degrees in an inductor. |
| Flow of current | There is no current flow between the parallel plates of the capacitor. | There is a flow of current through the coil of wire in an inductor. |
| Measurement unit | The SI unit of measurement for capacitance is Farad (F). | The SI unit of measurement for inductance is Henry (H). |
| Series combination | The expression for the parallel arrangement of capacitors in a circuit is as follows. | The expression for the parallel arrangement of inductors in a circuit is as follows. |
| Parallel combination | The expression for the series arrangement of capacitors in a circuit is as follows.  | The expression for the series arrangement of inductors in a circuit is as follows.  |
| Form of stored energy | A capacitor stores energy in the form of electric field. | An inductor stores energy in the form of magnetic field. |
| Stored Energy | The stored energy in a capacitor is given as follows.  | The stored energy in an inductor is given as follows. |
| Opposing voltage/current | A capacitor opposes a change in voltage. | An inductor opposes a change in the current. |
| Applications | Capacitors find their applications in storing memories in large computers, filters, power factor correction, etc. | Inductors find their applications in Televisions, automobiles, radios, etc. |
Conclusion
In conclusion, both capacitors and inductors are passive components that store energy in different forms. But besides this, there exist several differences between these two devices such as their working principle, construction, energy storage, behavior in AC and DC circuits, and applications that set them apart.
The most prominent difference between them is that a capacitor stores electric charge in the form of an electrostatic field, while an inductor stores magnetic energy in the form of an electromagnetic field. Therefore, based on the specific application, we can choose between an inductor and a capacitor based on the factors and differences highlighted in this article.
