What Is Inductor? - Definition From - TechTarget

Inductors and inductance

If the flow of current remains in a steady state, it passes through the inductor just like any wire without any reaction on the part of the inductor. However, if there are sudden changes in the current, the inductor tries to resist them.

An inductor causes the current to lag behind the voltage because of its magnetic field. When the current changes, the inductor's magnetic field changes -- increasing if the current increases, decreasing if the current decreases. Changes in the magnetic field cause changes to the magnetic flux, which in turn induce an electromagnetic field (EMF) that tries to oppose the change in current. If the current decreases, the EMF attempts to increase it. If the current increases, the EMF attempts to decrease it.

The inductor's ability to resist changes to the current is referred to as its inductance, which is the ratio of voltage to the current's rate of change within the coil. The standard unit of inductance is the henry (H). Because the henry is such a large unit, many inductors are measured in smaller quantities, such as the millihenry (1 mH equals 10-3 H) and the microhenry (1 µH equals 10-6 H). The nanohenry is occasionally used (1 nH equals 10-9 H).

Many factors can affect an inductor's level of inductance, including the number of coils, the length of the coiled wire, the material used for the core, and the size and shape of the core. If no core is used, then inductance also depends on the radius of the coil.

For a given coil radius and number of turns, air cores -- those without solid cores -- offer the least inductance. Materials such as wood, glass and plastic -- known as dielectric materials -- are essentially the same as air in terms of inductance. Ferromagnetic substances such as iron, laminated iron and powdered iron increase the inductance. In some cases, this increase is on the order of thousands of times. The shape of the core is also significant. Toroidal or donut-shaped cores provide more inductance for a given core material and number of turns than solenoidal or cylindrical cores.

Fabricating inductors onto integrated circuit (IC) chips is difficult, but it can be done, although they have a fairly low inductance. In some cases, inductance can be simulated by using transistors, resistors and capacitors fabricated onto IC chips.

Inductors share many elements in common with electrical transformers. They use wound coils and ferrous cores to create electromagnetic fields to store and convert electrical energy.