Some electrical components are built into circuits as a ‘passive component’, ie. they don’t need a connection to an independent electrical power source in order to operate their function, and they don’t generate or amplify power, instead they only receive energy, which they then can use in a variety of ways according to their design. Resistors and capacitors are passive components, and so is an inductor.
What does an inductor do?
An inductor – also known as a coil, reactor or a choke – is a small, two terminal component which usually consists of an insulated wire wound into a coil. An inductor opposes sudden changes in current flow, so it can slow down any current spikes or surges in a circuit and helps to keep current flow constant. This ability is called ‘Inductance’ and is measured in a unit called Henry (H), named after the 19th century American scientist Joseph Henry.
There are typically two types of inductor, a ‘surface mounted inductor’, which sits on pads on top of a printed circuit board and is attached with solder. And a ‘through hole inductor’, which is also mounted on top of a circuit board, but has a lead which is fed through via holes in the circuit board, before also being soldered on to the board.
How does an inductor work?
An inductor is able to control surges and spikes in current flow by storing energy in a magnetic field, before then releasing it back into the circuit. When current flows through the inductor, a magnetic force is generated around it in the direction of the right-handed thread. When current flows through the inductor with a conductor wrapped around it in the same direction, the magnetic force generated around the wire is bound together and becomes an electro magnet. The magnetic field of the inductor can change as the magnet is moved closer or further away.
The design of the inductor means it can pass DC current easily, but has difficulty in passing AC current. An inductor will suppress the waves of AC current and transform it into a smoother current. This enables an inductor to have a purpose in power supply circuits for electrical circuits running on DC currents.
Common uses of inductors in electronics
So we have established that an inductor is able to develop electromagnetic force in a certain direction and that this reduces fluctuations when it meets a fluctuating current flow. It can also store electric energy as magnetic energy. The high resistance to high frequency currents, coupled with the characteristic of allowing DC current to flow more easily, also means inductors can be used in various applications, most commonly in analogue circuits and signal processing. These applications include:
- Filtering signals by dividing them into necessary and unnecessary signals
- Smoothing current flow in a power circuit and therefore stabilising the voltage
- Use in high frequency circuits for matching impedance
- Storing and transforming energy in power converters
- When two or more inductors are located in close proximity and they both have coupled magnetic flux, this creates a mutual inductance, which in turn forms a transformer. This design is an essential component of every electric utility power grid.
Please note that this section is for information purposes only. Anyone using equipment referred to in this section must be suitably qualified and/or experienced within the respective field. If in doubt before use, please consult a qualified electrician or engineer & thoroughly read all instruction booklets.