A photoresistor is a light-dependent resistor which slowly loses its resistance when exposed to high levels of ultraviolet light. As a result, photoresistors convert light energy into electrical energy. Photoresistors are used in a wide variety of devices to detect the presence of light, control a device, or activate a system. They are usually dependent on external light sources, although they can be connected to a system that produces its own light. Photoresistors are generally made of cadmium sulfide but can be mixed with impurities to allow lower frequencies of light Read More

A rectifier changes alternating current into direct current. This process is called rectification. The three main types of rectifier are the half-wave, full-wave, and bridge. A rectifier is the opposite of an inverter, which changes direct current into alternating current. Half-Wave Rectifier The simplest type is the half-wave rectifier, which can be made with just one diode. When the voltage of the alternating current is positive, the diode becomes forward-biased and current flows through it. When the voltage is negative, the diode is reverse-biased and the current stops. The result Read More

A rheostat is an electrical component that has an adjustable resistance. It is a type of potentiometer that has two terminals instead of three. The two main types of rheostat are the rotary and slider. The symbol for a rheostat is a resistor symbol with an arrow diagonally across it. Rheostats are used in many different applications, from light dimmers to the motor controllers in large industrial machines. Rheostat Construction Most rheostats are the wire-wound type that have a long length of conductive wire coiled into a tight spiral. The Read More

A relay is a remote switch controlled by current, magnetism, or temperature. The relay was invented in 1835 by Joseph Henry (1979-1878), an American scientist. Relays are a common component in many devices, and there are many different types of relays. Relay Types The two main types of relay are electromechanical and solid-state. Electromechanical relays have a moving plate with contacts on it, while solid-state relays work similar to transistors and have no moving parts. Power relays use an electromagnet to move a set of contacts. The contacts are pulled Read More

An electrical shunt is a component used to transfer currents away from parts of a circuit. Components used as shunts include the resistor, capacitor, diode, and gas discharge tube. The main uses for electrical shunts are to reduce current load in meters, filter out high frequencies, and protect circuits from surges. The term shunt is also used in other fields, such as medicine, to describe non-electrical devices that perform a bypass function. Shunt Types Shunt resistors, also called bypass resistors, are large metal components with very low resistance. They look Read More

A thyristor is a solid state semiconductor device that consists of four alternating layers of N-type and P-type material. Many sources consider thyristors to be the same as Silicon Controlled Rectifiers (SCRs). In some cases they are defined as a large group of devices – the eligibility criterion being that the device should consist of a minimum of 4 layers of alternating N and P-type material. A thyristor functions as a bistable switch, which means that it starts conducting when its gate receives a pulse of current. It conducts until the Read More

A TRIAC is used in AC power control applications in order to switch high voltages over both parts of the AC waveform. As a result, TRIAC circuits are used in a number of applications that require power switching. The TRIAC was developed after the thyristor, which controls AC current over one half of the cycle. The TRIAC circuit can be visualized as two thyristors that are opposite, parallel, and have the two gates connected together with one device’s anode connected to another’s cathode. A common household device that uses the Read More

The Nixie tube, also called a counting tube, is a gas discharge tube used to display information. It is the predecessor of the light emitting diode and the liquid crystal display, both of which use less power and last longer than the Nixie tube. Although they are still made today, Nixie tubes have largely disappeared from modern electronics. History The idea of using a gas discharge to display information first appeared in the 1920s, but it wasn't until the 1950s that Nixie tubes became widespread. The term is actually a Read More

A potentiometer, called pot for short, is an electrical component that acts as a variable voltage divider. They usually have three terminals, one of which is connected to a moving center contact. A potentiometer with two terminals is a variable resistor, called a rheostat. Potentiometers come in many forms including rotaries, trimmers, sliders. Potentiometer is also the term for an old instrument that measured an unknown voltage after being calibrated with a known voltage. These have been replaced by multimeters today. Potentiometer Types Rotary potentiometers have a semi-circular contact made Read More

An inductor is a conducting coil, wrapped around a core, that creates inductance when an alternating current flows through it. Inductors are used to impede the flow of current in a circuit. The conductor is usually thin magnet wire, and the core is usually air or steel. Working of an Inductor When the alternating current flows through an inductor, it creates an electromagnetic field. The strength of this field depends on number of coils, the coil diameter and the permeability of the core material. Steel has a much higher permeability Read More