Introduction to Electronics - Inductors

Inductors are electrical components that can store energy in the form of magnetic fields. They consist of a metal filament wound around a ferromagnetic core. These components are also commonly called coils.

The operation of inductors, in simple terms, is to prevent sudden changes in current. Its SI unit of measurement is Henry (H), which measures the inductance of the inductor. Inductance is generally represented by the letter L. The symbol for an inductor is a coil, or a wound wire, as shown in the image below.

Just as capacitors store energy in the form of an electric field and "delay" the change in voltage, inductors do the same with current. This is because the current, when passing through the inductor coil, generates a magnetic field, which is stored by the core. However, the variation in this generated magnetic field induces an electromotive force (a voltage) in the coil, directly influencing the current in the coil. The current (I) generates a magnetic field (B), and the variation in this magnetic field generates current.

Therefore, just like capacitors, inductors do not have a constant behavior over time. Their response to applied inputs takes a certain amount of time to reach a steady state.

Inductors Formulas

The main formula of inductors is:

That is, the inductor voltage (Uꮮ) is equal to the inductance (L) multiplied by the time derivative of the inductor current (Iꮮ).

To understand better, let's simulate an inductive circuit, with a 10Ω resistor and a 1H inductor in series.

The image below shows the inductor current. When a voltage is suddenly applied to this component, the current takes a while to increase. In around 0.5s, the voltage reaches its final value.

To explain this phenomenon, let's analyze the voltages across the two components. In the image below, the blue line represents the inductor voltage, while the green line represents the resistor voltage. It is worth noting that the input voltage (5V) is equal to the sum of the inductor and resistor voltages. We can see that, as soon as 5V is applied, the inductor voltage goes to 5V and the resistor voltage remains at 0V. In other words, the inductor consumes all the voltage applied to the circuit.

This occurs because, when 5V is applied, there is a small variation in the current and, consequently, in the magnetic field of the inductor. According to the formula above, the variation in the current (or derivative of the current) generates a voltage in the inductor. This voltage consumed by the inductor causes the voltage in the resistor to be lower, decreasing the current of both components.

We can also see that, after a while, the voltage consumed by the inductor reaches 0V. In other words, at the beginning, the inductor acts as an open circuit and, at the end, it acts as a short circuit. This is the opposite behavior of capacitors.

In short, adding the inductor prevents the current from changing abruptly. If only a resistor were added, the current would jump from zero to its final value instantly. But in this case, the inductor prevents this.

Inductors Association

Just like with resistors and capacitors, it is possible to make associations of inductors in series and in parallel.

Serial Association

The equivalent inductance of inductors in series is found by the formula:

Parallel Association

The equivalent inductance of inductors in parallel is calculated as:

It is noted that the inductor associations have the same formulas as those of resistors.

Conclusions

In conclusion, inductors are essential components in many electrical and electronic systems, playing a crucial role in the control and storage of magnetic energy. Their ability to withstand changes in electrical current and their usefulness in filtering, oscillating, and power transformation circuits make them indispensable in a wide range of applications, from power supplies to communication systems.

Understanding the operating principles, characteristics and applications of inductors is essential for the development of innovative and efficient technologies. Thus, continuous research and improvement of these components will contribute to the advancement of technological solutions, reflecting their importance in the current scenario of electrical and electronic engineering.