What are Passive Electronic Components?

When it comes to electronic components, parts are either categorized as active or passive based on their ability to control or amplify power flow in a circuit. Since active components are used to manipulate the flow of electricity, they require a source of energy such as a direct current to perform their function. This article will focus on passive components, explain their function, and describe the different types: resistors, capacitors, inductors, and transducers.

Resistors are passive electronic components that work to reduce the flow of electrons traveling through a circuit. The resistance is measured by the unit ohm and is calculated by the famous Ohm's law, which states R (resistance) = V (voltage) / I (current). They are typically used for surge protection to limit current that may destroy sensitive electronic devices or any other application in which one must change the behavior of current. Resistors are considered fixed or variable depending on their ability to change resistance values based on external stimuli. Fixed resistors are commonly made of carbon or metal oxide, and their resistance value cannot be changed. This can become costly as the entire resistor would need to be replaced if there is a need to change resistance. Variable resistors are very common and can be found in devices such as car radios for volume control.

The next commonly found type of passive device is called a capacitor. Capacitors are devices that can store electrical energy in an electric field. They are designed with two conductive regions that are separated by a non-conductive region. When a battery is connected to a capacitor, the two opposing sides will become oppositely charged, creating an electric field. Even though a battery is used to charge capacitors, they remain passive components as no other energy source is required to keep them working. Capacitors are found in a variety of electronic devices and perform different functions. Most commonly, capacitors store energy that must be released suddenly, such as in a camera's flash circuit. Additionally, they are used in sensors, fusion research, and current smoothing.

Inductors are electromagnets that are used to slow down surge spikes and temporarily store energy. They are composed of a metal coil that creates a magnetic field as a current runs through it. The strength of the magnetic field is proportional to the amount of current passing through the coil. These magnetic fields store energy as potential energy and release it back into the circuit as needed to stabilize the current. Inductors, like capacitors, can be used as energy storing devices and can be found in components within computers. Another well-known application of inductors is in induction motors. Induction motors are designed with two coils that create opposing magnetic fields which move the rotor. Lastly, inductive loops are found under roads where there is a traffic light. When a car stops over these inductors, the coil's inductance will increase, sending a signal to the traffic light that there is a vehicle waiting.

Finally, transducers convert energy from one form to another, such as the sound waves from microphones being turned into electric signals for amplifiers. Transducers can be active or passive, and the passive variant uses some of the properties mentioned above, such as induction, resistance, and capacitance, to change the physical properties of the transducer. There are dozens of applications that can use transducers, but common ones are loudspeakers, fluorescent lamps, cathode ray tubes, and radio transmitters.



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