A passive component is an electronic component that can only receive energy, which it can either dissipate, absorb or store in an electric field or a magnetic field. Passive elements do not need any form of electrical power to operate.
Passive components are the cornerstone of all electronics, both physical design and the language of circuit models that describe electrical behavior in more complex systems. Many integrated circuits include passive electronic components, and many circuit boards contain some discrete passive components used for everything from power conversion to power stability, filtering, and configuring integrated circuits.
There are two types of passive components, dissipative and lossless. An example of a dissipative is a resistor, which cannot absorb power from an external circuit. Lossless does not have an input or output power flow. Examples of these would be Gyrators, transformers, and capacitors.
The electronic apparatuses we encounter are driven and held by the flow of electrical current via electronic circuits. Each circuit is an array of electrical elements designed to perform specific functions. According to the tasks, the system must perform, circuits carry out various operations, from simple actions to complex tasks.
Common examples of passive components include:
An inductor is also considered a passive element of a circuit because it can store energy as a magnetic field and deliver that energy to the circuit, but not continuously. An inductor’s energy-absorbing and delivering capacity is limited and transient in nature. For that reason, an inductor is known as a passive element of a circuit.
A transformer is an electrical device that transfers energy between two or more circuits through electromagnetic induction. When transformers step up, voltage, power, and energy remain the same on the primary and secondary sides. A varying current in the transformer’s primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varying electromotive force or voltage in the secondary winding.
A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. Resistors can only receive energy to scatter as heat as long as current flows through it and, at the same time, act to lower voltage levels within circuits. In electronic circuits, resistors restrain current flow, revise signal levels active bias elements, terminate transmission lines, among other uses. High-power resistors dissipate many electrical power watts as heat and are used as motor controls, power distribution systems, or generator test loads. Resistors may have fixed resistances that only change a little with temperature, time, or operating voltage. Variable resistors adjust circuit elements or sensing devices for heat, light, humidity, force, or chemical activity.
A capacitor is a passive two-terminal electrical component storing energy electrostatically in an electric field. The energy dealing capacity is limited and transient, though not supplying energy, instead of storing it for later use. They are also be used to differentiate between high-frequency and low-frequency signals. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric. The conductors can be thin films, foils, sintered metal beads, conductive electrolytes, etc. The “nonconducting” dielectric acts to increase the capacitor’s charge capacity. A dielectric can be glass, ceramic, plastic film, air, vacuum, paper, mica, oxide layer, etc. Many capacitors are available, including electrolytic capacitors, primary parallel-plate capacitors, and mechanical variable capacitors.
Typical applications of active and passive components
We are surrounded by these tiny electronic elements in everyday life. They are hidden inside lights, sound systems, computers, phones, cars, and many more. By definition, active components are found in every electronic device, so they have countless use cases. Classic examples include any device with computing power (integrated circuits), a built-in battery or display device, and LED lights (light-emitting diodes).
When it comes to passive components, incandescent light bulbs are a great example of transducers in action – they convert electrical energy into light and heat energy. Loudspeakers use transducers to convert electrical input into mechanical output, causing the cones inside the speakers to vibrate, thereby generating sound waves that we can hear. Sensors are another type of transducer that has long been used in scientific research and which are becoming increasingly ubiquitous through the ‘stratification’ of countless appliances and machines.
Other passive component use cases include microwave and radio frequency applications such as remote keyless entry systems, which rely on inductors. Antennas are also passive and are found in radios, GPS devices, satellites, wireless modems and routers, public transport, and more.