Inductance is a property of an electronic circuit that prevents current from changing. It's important to note the physical meaning of the word "change," a bit like inertia in mechanics. An inductor coil is used to store energy in a magnetic field, and you will find this phenomenon very important.
To understand the concept of inductance, three physical phenomena must be understood:
1. When a conductor moves with respect to a magnetic field, an electric current is induced in the conductor. This produces an induced electromotive force at both ends of the conductor.
2. When a conductor is in a changing magnetic field, an induced current is generated inside the conductor. As in the first case, there is an induced electromotive force in the conductor.
3. When an electric current flows in a conductor, a magnetic field is generated around the conductor.
Lenz's law. The induced electromotive force in a circuit is a physical quantity that describes the circuit to cancel or compensate for its own increase or decrease.
Based on this principle, there will be the following effects:
A An induced current will be generated whether the conductor and the magnetic field move relative to each other or the magnetic field changes. The direction of the induced current is opposite to that of the original magnetic field.
B When the current in a conductor changes, the magnetic field excited by the current will change. The change in the magnetic field will induce a new current to block the change of the original current.
C The electromotive force caused by a current change is opposite to the polarity of the potential producing the current change.
The unit of inductance is heng E (H). If the current in the conductor changes at a rate of IA/s, the electromotive force of IV will be induced, then the inductance of the conductor will be 1H.
This relation can be expressed as :V=L(δ I/ δ T), where V is the induced electromotive force, V; L is inductance, H; R is the current, A; T is time, s; △ is a small change.
This unit is suitable for inductors used in continuous filter cavities powered by DC power, but it is too large in dimension for RF and if circuits. The auxiliary milliheng (mH) and microheng (μH) units are commonly used in these circuits.
The conversion relation between them is: 1H=1000mH=1000000μH
So :1mH = 10-3h, 1μH = 10-6h
There is a remarkable phenomenon called self-induction: when the current in the circuit changes, the magnetic field excited by the current also changes, and the change in the magnetic field induces a reverse current that blocks the original current.
This induced current also produces an electromotive force, called the reverse emf. As with other forms of inductance, the units of self - inductance are E and its auxiliary units.
Although the concept of inductance refers to a range of phenomena, when used alone it is usually referred to as self-induction. Therefore, unless otherwise specified (mutual inductance, etc.), inductance in this chapter refers to self-inductance. Just remember: there is more to this term than is generally understood.
Post time: Jan-11-2020