Inductance is a fundamental parameter in the field of electricity and magnetism. It describes the ability of a circuit element, typically a coil or an inductor, to oppose changes in the current flowing through it. Inductance is denoted by the symbol "L" and is measured in units called henrys (H).
When the current through an inductor changes, it induces a voltage across the inductor according to Faraday's law of electromagnetic induction. This induced voltage is proportional to the rate of change of current and the inductance of the coil. Mathematically, this relationship can be expressed as:
=
−
V=−L
dt
di
Where:
V is the induced voltage across the inductor (in volts).
L is the inductance of the coil (in henrys).
dt
di
is the rate of change of current (in amperes per second).
Key points about inductance:
Self-Inductance: When the changing current flows through the inductor itself, it induces a voltage that opposes the change in current. This property is known as self-inductance.
Mutual Inductance: Inductance can also occur between two separate coils or circuit elements. When the changing current in one coil induces a voltage in another nearby coil, it is referred to as mutual inductance.
Energy Storage: Inductors store energy in the form of a magnetic field when current flows through them. The energy stored in an inductor is given by
=
1
2
2
E=
2
1
LI
2
, where
I is the current flowing through the inductor.
Time Constants: Inductors have an associated time constant,
=
τ=
R
L
, where
R is the resistance of the circuit. This time constant describes how quickly the current in the inductor reaches its steady-state value after a change.
Applications: Inductors are used in various applications, including filtering out high-frequency noise in circuits (as part of low-pass filters), in power supply circuits, transformers, and more.
Inductive Kick: When a circuit containing an inductor is suddenly interrupted, the inductor resists the change in current, leading to a voltage spike known as an "inductive kick" or "back EMF." This effect is important to consider when designing circuits.
Inductance plays a crucial role in understanding and designing electrical circuits, especially those involving changing currents or magnetic fields. It is an essential concept in electronics, electromagnetism, and electrical engineering.