Capacitor and Inductor

A capacitor is an important component in both digital and analogue electrical circuits. It allows for signal filtering and serves as a basic memory component.

A capacitor is an electrically charged element that retains energy. A coil that stores energy in a magnetic field is known as an inductor.

Capacitor 

A capacitor is a device that stores electrical energy in an electric field. It’s a two-terminal passive electrical component.

The operation of a capacitor is referred to as “capacitance.”. While there is some capacitance between any two electrical conductors in close proximity in a circuit A capacitor is a component that is used to increase the capacitance of a circuit. The capacitor was originally known as a condenser. Condenser microphones, also known as capacitor microphones, are one notable exception. This name and its cognates are still widely used in many languages, but only rarely in English.

Inductor

When electric current travels through it, an inductor, also known as a coil, choke, or reactor, stores energy in a magnetic field.  An inductor is made out of a coil of insulated wire.

The time-varying magnetic field provides an electromotive force when the current flowing through the coil varies (e.m.f.) (voltage) in the conductor, according to Faraday’s law of induction. According to Lenz’s law, the induced voltage has a polarity (direction) that is opposite to the current shift that created it. Inductors, as a result, resist all current fluctuations that flow through them.

Symbol of inductor and capacitor

Fig: capacitor and inductor symbol

Impedance and reactance

Only the resistance of an element in a DC circuit can be used to describe it. In a DC circuit, a capacitor’s resistance is treated as an open connection (infinite resistance), but an inductor’s resistance is regarded as a short connection (zero resistance). In other words, in an ideal DC circuit, utilising capacitors or inductors would be a waste of components. Despite this, they are nevertheless employed in practical circuits since they never function with ideal constant voltages and currents.

In contrast to constant voltage circuits, the impedance of an element in an AC circuit is a measure of how much it resists current flow when an AC voltage is put across it. It’s essentially a voltage-to-current ratio in the frequency domain. Impedance is a two-part complex number: the real part and the imaginary part:

Z=R+jX

The complex impedance is denoted by the letter Z. Resistance is represented by the actual part R, while reactance is represented by the imaginary part X. Reactance can be either positive or negative, whereas resistance is always positive. In a circuit, resistance loses power as heat, whereas reactance stores energy as an electric or magnetic field.

Impedance of a capacitor

Capacitors are electronic components that add capacitance to a circuit. They’re used to store electrical energy in the form of an electric field for a short period of time. While theoretically valid, this definition means little to a hobbyist or even most engineers. In the time domain, it’s probably more accurate to say that capacitors are used to lag the voltage by 90 degrees compared to the current. 

For the capacitor impedance, the following equation is used to represent this fact using complex numbers:

Zc=-jωC

where Zc is the capacitor’s impedance, is the angular frequency (given by =2f, where f is the signal’s frequency), and C is the capacitor’s capacitance. This formula alone reveals a number of facts:

An ideal capacitor has zero resistance.

For all frequency and capacitance values, the reactance of an ideal capacitor, and hence its impedance, is negative.

The effective impedance (absolute value) of a capacitor is proportional to its frequency, and it always decreases with frequency for perfect capacitors.

Impedance of an inductor

Inductors, on the other hand, are components that add inductance to a circuit. They’re used to store electrical energy in the form of a magnetic field for a short period of time. Inductors are used to lag the current by 90 degrees in the time domain when compared to the voltage. 

The impedance of an inductor is calculated using the following equation:

ZL=jωL

where ZL is the inductor’s impedance, is the angular frequency, and L is the inductor’s inductance. From this formula, numerous inferences can be drawn:

A perfect inductor has zero resistance.

For all frequency and inductance values, the reactance of an ideal inductor, and hence its impedance, is positive.

An inductor’s effective impedance (absolute value) is proportional to its frequency, and for ideal inductors, it always rises with frequency.

Applications of capacitor

In any electrical apparatus, capacitors are a common component. There aren’t many circuit boards that don’t include a capacitor. Ceramic, electrolytic, tantalum, polyester, and other dielectric materials are used to construct them.

Ceramic capacitors are commonly utilised for decoupling or bypassing on an integrated circuit’s power supply pin (IC). They also keep stray RF waves from interfering with the voltage supply.

Electrolytic capacitors are utilised in circuits and power electronics where high power consumption is required.

Tantalum capacitors: Due to the use of tantalum, these capacitors can have a higher capacitance value while being packaged in a smaller box. They also have a more consistent behaviour and reduced leakage currents.

Applications of inductors

Inductors are utilised in a variety of applications as one of the most fundamental passive components.

Filters: Inductors are frequently used in conjunction with capacitors and resistors to construct filters for analogue circuits and in-signal processing. When employed alone, inductors operate as a low-pass filter. When capacitors, inductors, and resistors are used together, complicated filters are created that can be employed in a variety of applications.

Motors: Inductors are fixed in situ and cannot be moved or aligned in magnetic fields nearby. Electrical energy is converted into mechanical energy by induction motors. The alternating current’s magnetic field aids in the rotation of the shaft in motors.

Transformers is a well-known application. A transformer is made up of inductors that share the same magnetic path.

Inductors can be utilised as a kind of energy storage. They do not retain energy for a long time, unlike capacitors. Energy is stored in the form of the magnetic field in inductors, however this fails when there is no power source.

Conclusion 

A capacitor is an electric circuit element that is used to temporarily store electrical energy (charge) between two parallel conductor plates separated by a non-conductive zone separated by an electric field. Inductors are one of the three passive linear circuit elements that make up electronic circuits, along with capacitors and resistors. Inductors are common in alternating current (AC) electronic equipment, especially in radio equipment.