Inductors are electronic components that regulate and distribute the signal they receive, and make sure it reaches its intended destination in a steady flow. To achieve this, they store energy in magnetic fields. If a person deliberately brings the magnetic field of two inductors attached to two different circuits together, the inductors can transfer energy from one to the other through their magnetic fields. When inductors are used like this they are called a "coupled inductor."
This energy transfer between a coupled inductor allows people to charge mobile devices like phones, music players, and other small devices with rechargeable batteries. Increasing magnetic field strength increases the amount of energy that can be transferred. This can be accomplished by increasing the number of coils in the inductors, increasing the overall size of the coils, and adding a metal core to the coils. Usually a core made of iron is used for this purpose.
To control the amount of energy that inductors send to electronics, switches are used. These quickly alternate on and off, stopping the flow of electricity into inductors and allowing it to be stored in a magnetic field for brief amounts of time. More electricity is lost the longer it is stored, so the longer a switch is off the lower the amount of power is being supplied. This is known as the switch frequency and it is customized to meet the needs of specific electronics.
Inductors allow a wide range of electricity to be transferred, and inductive coupling is used in all power transformers, from the large ones that deliver power to peoples’ houses, to small ones used in almost all electronics. A transformer relies on a coupled inductor to regulate the power that it distributes and to protect against power surges and fire hazards. Inductors are also used in electric motors and generators.
The magnetic field of a coupled inductor can also be used in creating a sensor. These are useful in mechanical settings to control the positions of machine parts. Other uses of sensors include the identification chips that help find lost animals and the anti-theft devices used in some stores. Traffic lights are also sometimes aided by the use of a coupled inductor. Inductors that are concealed just below the pavement react with the metal in vehicles, signalling the light to change when cars are waiting.
Due to the number of uses that coupled inductors have for meeting people's electrical needs, they will likely continue to be used for a long time. There are some electronic devices that do not use inductors. They are called non-isolated electronics and include old televisions and radios, and some newer computer components.