Inductors are passive electronic components that store energy in their magnetic field when an electric current flows through them. They are often used in electrical and electronic circuits to oppose changes in current, filter signals, and store energy. An inductor typically consists of a coil of conductive wire, which may be wound around a core made of air, ferrite, or another magnetic material.
The key property of an inductor is its inductance (L), which is a measure of its ability to oppose changes in current. Inductance is measured in henries (H) and depends on factors such as the number of turns in the coil, the coil’s geometry, the spacing between the turns, and the core material (if any).
Energy stored in an inductor
The energy stored in an inductor is due to the magnetic field created by the current flowing through it. As the current through the inductor changes, the magnetic field also changes, and energy is either stored or released. The energy stored in an inductor can be expressed as:
W = (1/2) * L * I^2
where: W = Energy stored in the inductor (joules, J) L = Inductance of the inductor (henries, H) I = Current through the inductor (amperes, A)
This formula shows that the energy stored in an inductor is directly proportional to its inductance and the square of the current flowing through it. If the current through the inductor is constant, the energy stored remains constant as well. However, when the current changes, the energy stored in the magnetic field will also change, and this can lead to energy being either absorbed or released by the inductor.
Inductors store energy in their magnetic field, making them useful in various applications, such as energy storage systems, DC-DC converters, and switching regulators. In these applications, inductors work in conjunction with other components, like capacitors and diodes, to store and release energy, helping to maintain a stable output voltage or current.
Hydraulic Analogy
The hydraulic analogy, or the electric-fluid analogy, is a widely used analogy between hydraulics and electricity, which is a useful tool for teaching and for those who are struggling to understand how circuits work. it can also be applied to heat transfer problems.
Since electric current is invisible and the processes in play in electronics are often difficult to demonstrate, the various electronic components are represented by hydraulic equivalents. The relationship between voltage and current is defined (in ohmic devices like resistors) by Ohm’s law. Ohm’s Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems.
Electricity (as well as heat) was originally understood to be a kind of fluid, and the names of certain electric quantities (such as current) are derived from hydraulic equivalents.
- Voltage is like the pressure difference that pushes water through the hose. It is measured in volts (V). This model assumes that the water is flowing horizontally so that the force of gravity can be ignored.
- Current is equivalent to a hydraulic volume flow rate; that is, the volumetric quantity of flowing water over time. Usually measured in amperes. The wider pipe is, the more water will flow through. It is measured in amps (I or A).
- Inductors are equivalent to a heavy paddle wheel placed in the fluid flow. The mass of the wheel and the size of the blades restrict the water’s ability to rapidly change its rate of flow (current) through the wheel due to the effects of inertia, but, given time, a constantly flowing stream will pass mostly unimpeded through the wheel, as it turns at the same speed as the water flow.
