What Is the Difference Between Inductor & Capacitor?

Understanding Two Small Components That Do Very Different Jobs

Consider what occurs once you turn on your television or plug your computer into an electric charger. Your TV or laptop begins to function, its screen becomes active, but all of this is done seemingly effortlessly. In reality, however, electrical energy is being constantly controlled and transferred within your device. Various small elements work together to supply the circuit with the needed amount of energy.

In this respect, inductors and capacitors may be mentioned as examples. Although you can find them placed quite close to each other on the circuit board, they differ in their approach to electrical energy storage. While one element will store the energy in a magnetic field, the other will use the electric field for that purpose.

Knowing the difference between an inductor and a capacitor is more than just knowing their definitions. Rather, it means understanding the process taking place in a circuit once the electrical energy is applied or transformed. After understanding the behavior of these two elements, you will start understanding many of the devices we use today.

What Is an Inductor and How Does It Work?

In most cases, an inductor consists of a wire wound up into a coil. As electricity moves through the wire, it produces a magnetic field around it. The inductor stores energy in the magnetic field produced and may be able to release the stored energy during the course of the circuit operations.

Consider what happens when one tries to move a very heavy shopping cart that is totally stationary. One needs to put in extra effort to start it off, and even after it gets started, any alteration in its movement is not easy. This is quite similar to the way an inductor behaves when it comes to electrical current.

This behaviour is described by a scientific relationship:

[
V_L=L\frac{dI}{dt}
]

In this case, the voltage across the ideal inductor is represented by (V_L), the inductor’s value is known as (L), and the rate of change of current is expressed as (dI/dt). This implies that, the faster the rate of change of current, the greater will be the voltage opposing it.

The value of inductance has units of henries (H) but it is quite common to use fractions of henries in the form of milli- or micro-henries in electronics. The stored energy in the ideal inductor depends on the inductance as well as the current flowing through the inductor.

[
E_L=\frac{1}{2}LI^2
]

This equation reveals a curious fact: if the current doubles and inductance remains unchanged, the energy stored will be four times greater because the current is squared in the formula.

Inductors are used in switching power supplies, DC-DC converters, and electronic filters. Their cores may be made of ferrite or any other magnetic materials, and the performance and the capacity of inductors depend on the core and winding design.

What Is a Capacitor and Why Is It Useful?

In contrast to a magnetic field operation, capacitors work on electric field principles. The fundamental structure of a capacitor includes two conducting plates placed apart with a non-conducting substance in between.

It could be compared to a tiny reservoir for storing water which can be used whenever needed; just like the water reservoir, a capacitor acts in storing charges of electricity; once the voltage is applied, the charge starts accumulating on the capacitor’s plates, and once the voltage is removed, the capacitor discharges the stored charge.

The charge stored in a capacitor depends on the capacitance and voltage across the capacitor.

[
Q=CV
]

This equation indicates that (Q) stands for electrical charge, (C) stands for capacitance while (V) stands for voltage. The measurement of capacitance is done using farads (F); however, microfarads, nanofarads, and picofarads are used in different technologies.

For instance, a capacitor having 100 microfarads of capacitance across an ideal five volts is able to hold 500 micro coulombs of charge.

The energy which is kept in a capacitor can be calculated in the following manner:

[
E_C=\frac{1}{2}CV^2
]

Capacitors, similar to inductors, have the ability to retain energy for a limited period of time and release the energy back into the circuit. The difference between them is in their reactions to voltage changes. While capacitors resist sudden changes in voltage, inductors are able to react to them.

The advantage of capacitors is used in many different electronic gadgets such as chargers, sound gadgets, computer systems, and many others. The common types of capacitors that are used are given below: Ceramic capacitors, Film capacitors, Electrolytic capacitors.

The Real Difference Between an Inductor and a Capacitor

In the beginning, you may think that these two parts are essentially doing the same thing since both have the ability to hold onto electricity. However, what makes them different from one another is the way in which each part stores the electricity and how each part reacts when changes occur with respect to the electrical condition.

An inductor has energy stored within a magnetic field created by the movement of electric current through the component. Conversely, a capacitor contains energy stored within an electric field created by the potential difference (voltage) across the capacitor's terminals. A key distinction between inductors and capacitors is that inductors resist quick changes in electrical current, whereas capacitors resist quick changes in electrical potential (voltage).

An electronics circuit is supplied with a constant stream of electrical energy through a power source. Rapid fluctuations in the rate at which electrical charge flows (current) are minimized with the use of an inductor. When the voltage being produced starts to fluctuate, capacitors can be used to regulate the fluctuations through their ability to store and release electrical energy charging and discharging.

In the beginning, both devices appear to do the same job of storing energy. The real difference, though, is in the method of energy storage and how the two devices respond to different electric signals.

The inductor stores energy in the magnetic field formed by the current. The capacitor stores energy in the electric field formed by the voltage. The inductor reacts to the fast and sudden change in current, whereas the capacitor reacts to the instantaneous change in voltage.

Let us take an example of a power supply system which is supplying the constant power to an electrical circuit. In case of sudden changes in current, the inductor would prevent such changes from happening. In case of fluctuation of voltage as a result of which output voltage starts fluctuating, the capacitor would help in providing smooth charging and discharging.

How Frequency Changes Their Electrical Behaviour

There is another kind of opposition to AC offered by an inductor. This is called inductive reactance, which varies with the frequency of the AC and the inductance of the inductor.

[
X_L=2\pi fL
]

A capacitor has capacitive reactance, which follows a different relationship.

[
X_C=\frac{1}{2\pi fC}
]

The letter (f) indicates frequency as measured in hertz in both equations. The main point to understand is that inductive reactance becomes higher as frequency rises, but the opposite can be said about capacitive reactance.

Let us imagine a perfect 10-mH inductor operating at 1,000 Hz. Its reactance will be equal to about 62.8 Ohm. With the increase of frequency to 10,000 Hz, the reactance will become about 628 Ohm.

Now let us look at a perfect capacitor having the capacitance of 10μF. Its capacitive reactance is 15.9 Ohm at the frequency of 1,000 Hz. At 10,000 Hz, capacitive reactance is going to drop to the value of 1.59 Ohm.

These examples show that these two elements can be good for controlling signals at different frequencies. The values of reactance are theoretical and do not take into account the impedance or other physical phenomena occurring with the real-life electrical components.

The timing, however, for those components is different in AC circuits, since with the ideal inductor, the current is delayed by 90 degrees in relation to voltage, while for the ideal capacitor it is ahead by the same value.

Why Engineers Often Use Both Components Together

Think about a switching power supply inside a computer. The supply continues to switch current to change power into something the computer can take advantage of. In this process of switching, variations in electrical power occur.

An inductor serves to slow down the change in current. A capacitor does the same with the change in voltage. When combined and properly connected, these elements will deliver a stable power output.

Besides, they can establish the so-called LC filter yielding inductance and capacitance effects. Thanks to these effects, the filter manages to influence the passage of frequencies in the circuit. The noise is eliminated and the necessary signal passes through.

Another remarkable application is the LC resonant circuit, where energy circulates between the inductor and the capacitor. In ideal conditions, the resonant frequency of the circuit can be calculated using the formula below:

[
f_0=\frac{1}{2\pi\sqrt{LC}}
]

The resonant frequency relies on the inductance and capacitance. Raising one of the components will reduce the resonant frequency, provided that the other component remains unaffected. This phenomenon is employed in RF circuit applications and other electronics that work with frequencies. Circuits also suffer losses due to resistance and other losses of energy.

What Matters When Choosing the Right Component?

When picking a component, one must think about more than just its metric. Engineers must analyze what sort of stress the component will receive during normal and extreme conditions of its operation.

The current rating of an inductor is vitally important. Too much current through the magnetic core can lead it into saturation, which can lead to the decrease in the inductance and increase the current unexpectedly fast.

The limitations of capacitors are slightly different. They require not only the right voltage rating but also have to account for the effect of excessive ripple current. Temperature is also important for its capacitance.

Perfect components do not exist as well. Inductors have wire resistance and stray capacitance between their coils. Capacitors possess both resistance and inductance as well. At high frequencies, they may impair performance.

When designing mass-produced electronic equipment, these nuances are important to consider as the component must function properly within the entire system. The CET Technology produces magnetic components, including inductors and transformers, that require special attention to component choice and electrical properties.

Conclusion

It is easy to see the differences between the two devices when looking at how they behave inside a circuit. While the inductor uses a magnetic field to store energy and opposes the changes in current, a capacitor uses an electric field for energy storage and opposes the changes in voltage.

The behavior of both devices depends on the frequency too. The higher the frequency, the higher reactance of an inductor, and vice versa for the capacitor. This feature of both devices is one of the reasons why they are used together in power supplies, filters, and signal-processing circuits by the engineers.

However, none of them works perfectly on their own. Every of these devices has some advantages and disadvantages. Provided that engineers understand the properties of these components and use appropriate component values, it will be easy for them to design a circuit that is going to function effectively. With a little coil and two plates, one can significantly affect the performance of an electronic appliance.