Inductance is a property of an electronic circuit to prevent current changes. Note that "change" the physical meaning of the term, it is very important, a bit like the mechanical inertia. An inductor coil is used to store energy in a magnetic field, you will find this phenomenon is very important. To understand the concept of inductance, we must understand three physical phenomena:
(1) When a conductor relative to the magnetic field movement, the conductor will be induced current. So that both ends of the conductor will produce induced electromotive force.

(2) changes when the conductor in a magnetic field, the induced currents generated inside the conductor. Like the first case, as the conductor will produce induced electromotive force.

(3) When a current flows in a conductor, generates a magnetic field around the conductor.

According to Lenz's law. Circuit described induced electromotive force is offset or compensated circuit of its own to increase or decrease a physical quantity. Starting from this principle, we have the following effects:

(1) whether there is relative movement of the conductor and the magnetic field or magnetic field changes, will generate induced current. Direction of the induced current trend is to the original magnetic field in the direction opposite to its excitation.

(2) conductors current changes, whereby the current excitation of magnetic field changes, changes in the magnetic field will induce a current in order to hinder the new changes in the original current.

(3) by the current change induced electromotive force generated current changes the potential of the opposite polarity.

Inductor unit is Henry E [Li] (H). If the current in the conductor to IA / s rate of change will be induced electromotive force IV, then the inductance of this conductor on the 1H. This relationship can be expressed as:

V = L (ΔI / Δt)

Wherein, V is the induced electromotive force, V; L is the inductance, H; r is the current, A; t is time, s; △ a minute amount of change.

Hang E [Li] This unit is suitable for use in the continuous filter chamber DC power supply inductor, but for RF and IF circuits, its dimension too. In these circuits commonly used auxiliary unit mH (mH) and micro-henry (μH). Conversions between them are:

1H = 1000mH = 1000000μH

and so,

1mH = 10-3H, 1μH = 10-6H

There is a noteworthy phenomenon is called self-inductance: When circuit current changes, the current excitation field changes accordingly. Changing magnetic field induces a reverse current will hinder change the original current. The induced current will produce a force, known as counter electromotive force. Like other forms of inductance and self-inductance of the unit is Henry E [Lee] and its subsidiary units.

While the concept involves a series inductance phenomenon, but usually refers to the self-inductance when used alone. Therefore, the discussion in this chapter unless otherwise stated (such as mutual inductance, etc.), all referring to the self-inductance inductance. But remember: this jargon has more than the commonly understood meaning.