# What is an inductance 1

## Coil / coils / inductance

A coil is an electronic component. A typical coil is a solid body around which wire is wrapped. However, this body does not have to be present. It usually only serves to stabilize the thin wire. The special property of a coil is its inductance. What capacitance is to a capacitor, inductance is to a coil.

### Inductance

Inductance is the ability of a coil to generate a voltage in its own turns using a magnetic field. It is said that the coil induces a voltage. The trigger is the voltage's magnetic field.

A coil has an inductance of 1 H if a self-induction voltage of 1 V is generated with a uniform current change of 1 A in one second.

The term inductance is generally used as an umbrella term for various coils.

### Unit and symbols

The symbol is the capital L. The inductance L has the unit Ωs. The unit Ωs has the designation H (Henry).
In electronics, small coils with a small inductance are usually specified in mH.

 Henry 1 H. 1 H. 100 H Millihenry 1 mH 0.001 H. 10-3 H Microhenry 1 µH 0.000001 H. 10-6 H Nanohenry 1 nH 0.000000001 H. 10-9 H

### Self-induced voltage

If a constantly changing current flows through a coil, a constantly changing magnetic field is created around the coil. Every change in the current or magnetic flux generates a self-induction voltage in the coil. This voltage is directed in such a way that it counteracts a change in current over a certain period of time. A decrease in the current leads to an increase in the voltage. And an increase in current leads to a decrease in voltage.

### Self-induced voltage

The self-induced voltage UL. is all the greater

• the greater the inductance L is.
• the greater the change in current ΔI is.
• the smaller the time Δt is the change in current.

The influence of the coil on the self-induction voltage is indicated by the self-induction coefficient. This is also called inductance.

### Circuit symbols

(outdated)
(outdated with iron core)

### Types

• Air core coil (wound wire)
• Iron core coil with sheet metal core, HF core or ferrite core

In addition to the cylindrical shape, coils are also available in a flat design and as a rectangular shape winding. And then there are also components that have a design-related inductive component. Because there are coils in a wide variety of designs and shapes, one generally speaks of an inductance.

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