How Do Inductors Behave? How Do You Protect Against Inductive Kick-Back?
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Inductors – Rate Of Current Change
Inductors are closely related to capacitors; the rate of current change in an inductor depends on the voltage applied across it, whereas the rate of voltage change in a capacitor depends on the current through it. The symbol and defining equation for an inductor is where L is called the inductance and is measured in henrys (or mH, uH, etc.) and “di/dt” is the change in current over a small period of time.
Putting a voltage across an inductor causes the current to rise as a ramp (for a capacitor), supplying a constant current causes the voltage to rise as a ramp; 1 volt across 1 henry produces a current that increases at 1 amp per second).
Inductor Symbols
The symbol for inductors looks like a coil of wire; that’s because, in its simplest form, that’s all it is. Variations include coils wound on various core materials, the most popular being iron (or iron alloys, laminations, or powder) and ferrite, a black, nonconductive, brittle magnetic material. these are all ploys to multiply the inductance of a given coil by the “permeability” of the core material. The core may be in the shape of a rod, a toroid (doughnut), or even more bizarre shapes, such as a “pot core” (which has to be seen to be understood).
Inductors find heavy use in radio frequency (RF) circuits, serving as RF “chokes” and as parts of tuned circuits. A pair of closely coupled inductors form the interesting object known as a transformer.
An inductor is, in a real sense, the opposite of a capacitor.
