Electronics/Inductor Construction

An inductor is the electrical equivalent of a flywheel. When you introduce energy to an inductor, the current flows slowly at first, just like a flywheel doesn't instantly get up to speed. And if you try to stop a flywheel instantly, something will break. If you let current through an inductor, then open the switch, the energy of the inductor must go somewhere - it will arc back across the switch, quickly ruining it - thus the condensor used in coil-type automotive ignition systems: it stores the energy until the inefficiency of the flywheel can turn it into heat.

Inductors are formed of a coil of conductive material. Normally they are made of copper wire, but not always (Example: aluminum wire, or spiral pattern etched on circuit board). The material around and within the coil affects its properties; common types are air-core (only a coil of wire), iron-core, and ferrite core. Iron and ferrite types are more efficient because they conduct the magnetic field much better than air; of the two, ferrite is more efficient because stray electricity cannot flow through it. Ferrite is more expensive but operates at much higher frequencies than iron cores.

Some inductors have more than a core, which is just a rod the coil is formed about. Some are formed like transformers, using two E-shaped pieces facing each other, the wires wound about the central leg of the E's. The E's are made of laminated iron/steel or ferrite.

Toroidal inductors are most efficient of all, they are wound around a donut shape which is made of ferrite. They are more difficult to make, because the formed coil cannot be manufactured directly on the toroid - it must be wound onto it.

Important qualities of angf inductor

There are several important properties for an inductor.
 * Current carrying capacity is determined by wire thickness.
 * Q, or quality, is determined by the uniformity of the windings, as well as the core material and how thoroughly it surrounds the coil.
 * Last but not least, the inductance of the coil.

The inductance is determined by several factors.
 * coil shape: short and squat is best
 * core material
 * windings: winding in opposite directions will cancel out the inductance effect, and you will have only a resistor.

(someone add formulas etc. for determining inductance, please.)