Various Types of Resistors with Diagrams

What are Carbon Composition Resistors?

  • Carbon composition resistor is also known as carbon composite otherwise carbon comp. This is an old type of resistor but used as a main resistor in many tube or valve-based devices such as radios, TVs, electronic devices, etc. 
  • The Carbon composition resistor function is, it is one kind of fixed resistor, used to restrict or reduce the flow of current to a certain stage.
  • Carbon composition resistors (CCR) consist of a solid cylindrical resistive element with embedded wire leads or metal end caps to which the lead wires are attached. 
  • The body of the resistor is protected with paint or plastic.
  • Higher concentrations of carbon, which is a good conductor, result in lower resistance.
  • Carbon composition resistors are very small in size and have less power loss. Also, the resistors can have a very high value even up to few megaohms. These are so small that we cannot even indicate the value with readable digits on it. 
  • For that, we use color codes on the resistor body to indicate the resistance value.

What are Wire Wound Resistors?

  • A wirewound resistor is an electrical passive device that limits or restricts current flow in a circuit.
  • The conductive wire can be made of varying alloys and thickness to control the resistance value.
  • Wirewound resistors are typically used in high power and industrial applications such as circuit breakers and fuses.
  • A resistor that is designed using a conductive wire to limit or restrict the flow of current within a circuit. The designing of this resistor can be done using a conductive wire by wounding around a non-conductive core. Generally, the material of the wire can be made with like Nichrome (Nickel-chromium alloy) or Manganin (copper-nickel-manganese alloy). 
  • These resistors generate very accurately, excellent properties for high power ratings & low resistance values. 
  • These resistors are used in industrial and high-power applications like fuses, circuit breakers. 
  • The wire-wound resistor symbol is similar to a normal resistor.
  • The wire wound resistor is manufactured by winding a length of resistive wire such as nichrome on to a round, hollow porcelain or ceramic core.
  • The ends of the winding are attached to metal terminals inserted in the core. The tinned copper wire leads are attached to these metal pieces.
  • This assembly is coated with enamel containing powdered glass. It is then heated to develop a coating known as vitreous enamel.
  • The cement or varnish can be used as a coating. This coating is very smooth and gives mechanical protection to the winding.
  • It also helps in conducting heat away from the unit quickly. In other wire wound resistors, a ceramic material is used for the inner core and the outer coating.
  • Some of the wire wound resistors are too heavy to be suspended by wire leads and therefore, must be mounted with bracket.
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What are Cement Oxide Resistors?


  • Cement resistors are power resistors that are heat and flame-resistant.
  • Cement resistors are made to handle a large amount of power flowing through it with it being undamaged by heat or flames. 
  • If you are designing a circuit where a lot of current is being passed through a resistor and with it needing to be resistant to high heat and flame, cement resistors is a good design choice.
  • Typical power ratings range from 1W to 20W or more.
  • Tolerances from the stated resistance value are around 5 percent.
  • cement Resistor are made by winding resistance wires around non-alkaline ceramic core, which is added with a layer of heat and humidity resistant and non-corrosive protective material. The wire wound resistor is then placed in a square ceramic package sealed with special nonflammable heat-resistant cement.
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What are the fusible resistors?


  • A fusible resistor opens like a fuse when its current rating is exceeded. 
  • The higher heat generated by the fusible resistor can damage other components and potentially lead to the ignition of nearby combustible components. 
  • The primary benefit of a fusible resistor is that its resistance limits inrush current.
  • Fusible film resistors are used in various low power and low surge applications. 
  • These include low-level fire safety, monitoring and management, high-end audio/video systems, environmental management controls and systems, and laser printers.
  • In WWF series, resistors up to 5W, the resistance value is colour coded with 3 bands plus a tolerance band. 
  • An additional white band indicates that the resistor is fusible. 
  • For resistors 6W and above, the value is printed on the resistor.
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What is Potentiometer?


  • A potentiometer (also known as a pot or potmeter) is defined as a 3 terminal variable resistor in which the resistance is manually varied to control the flow of electric current. 
  • A potentiometer acts as an adjustable voltage divider.
  • A potentiometer is a passive electronic component. Potentiometers work by varying the position of a sliding contact across a uniform resistance. 
  • In a potentiometer, the entire input voltage is applied across the whole length of the resistor, and the output voltage is the voltage drop between the fixed and sliding contact.
  • A potentiometer has the two terminals of the input source fixed to the end of the resistor. 
  • To adjust the output voltage the sliding contact gets moved along the resistor on the output side. 
  • Potentiometers are commonly used to control electrical devices such as volume controls on audio equipment. 
  • Potentiometers operated by a mechanism can be used as position transducers, for example, in a joystick.

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What are trimmers?

  • A trimmer potentiometer, also known as a trim pot, is a type of variable resistor or adjustable potentiometer that can adjust, tune, and calibrate circuits. 
  • These trimmer resistors are often used to initially calibrate equipment after manufacturing.
  • Potentiometers are variable resistors that feature an adjustable knob or dial used to change the location of the output contact. 
  • Trimmers are potentiometers that need infrequent adjustment. 
  • They are often used to calibrate a device or circuit after manufacturing, and often require a special tool for adjustment.
  • When they are used as a variable resistance (wired as a rheostat) they are called preset resistors. Trimpots or presets are normally mounted on printed circuit boards and adjusted by using a screwdriver.

What are rheostats?

  • Rheostats are two-terminal devices, with one lead connected to the wiper and the other lead connected to one end of the resistance track. 
  • The rheostat is a variable resistor whose resistance can be changed to change the current flowing amount through a circuit.
  • Rheostat, adjustable resistor used in applications that require the adjustment of current or the varying of resistance in an electric circuit. 
  • The rheostat can adjust generator characteristics, dim lights, and start or control the speed of motors.
  • Rheostat works on the principle of Ohm's law. Ohm's law states that current in a circuit is inversely proportional to the resistance at the given temperature.

What are SMD Resistors? 

  • The resistor which uses surface mount technology is known as an SMD resistor. 
  • These resistors are used in huge quantities. In most of the manufacturing industries, this technology is used. 
  • This technology improves by allowing high levels of automation, manufacturing, improves reliability, high range of functionality in small size, and decreases the cost drastically.
  • SMD resistors give low power dissipation, low stray capacitance, and low stray inductance.
  • SMD resistors are just one form of component that uses surface mount technology. 
  • This form of component technology has now become commonplace for manufacturing electronic equipment as it enables much faster and more reliable construction of electronic printed circuit boards.
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What are Varistors? 

  • A varistor is a 2 terminal semiconductor device that protects the electrical and electronic devices from overvoltage transients. Its resistance is dependent on the applied input voltage.
  • A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current-voltage characteristic that is similar to that of a diode.
  • This type is commonly known as the metal-oxide varistor (MOV).
  • Varistors are used to protect a circuit from high voltage surges. 
  • When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit.
  • When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit.
  • The word varistor is formed by combining variable and resistor. It is also known as a voltage-dependent resistor, VDR whose resistance changes automatically with the corresponding change in the voltage across it.
  • It is always placed in a shunt with the device being protected. This is basically done to protect the circuit from voltage surges.

What are carbon film resistors?

  • Carbon film resistors are a type of fixed value resistor. 
  • They are constructed out of a ceramic carrier with a thin pure carbon film around it. This carbon film functions as resistive material.
  • Carbon film resistors have low cost, poor electrical performance, and stability, and they are generally not suitable for general-purpose resistors. But because it is easy to make a high resistance film, it is mainly used as a resistor of high resistance and voltage, which is the same as high-voltage resistors.
  • Carbon-composition resistors are non-inductive and provide an adequate solution at low average power, but they can be unstable because of moisture or high voltage. 
  • Carbon-composition resistors rated at 2 W and higher are almost impossible to source.

What are thermistors?

  • A thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word is a combination of thermal and resistor.
  • Although all resistors’ resistance will fluctuate slightly with temperature, a thermistor is particularly sensitive to temperature changes.
  • Thermistors act as a passive component in a circuit. They are an accurate, cheap, and robust way to measure temperature.
  • While thermistors do not work well in extremely hot or cold temperatures, they are the sensor of choice for many different applications.
  • Thermistors have a variety of applications. They are widely used as a way to measure temperature as a thermistor thermometer in much different liquid and ambient air environments.

What are Photoresistors?

  • A photoresistor is a type of resistor whose resistance decreases when the intensity of light increases. 
  • In other words, the flow of electric current through the photoresistor increases when the intensity of light increases. 
  • Photoresistor changes its resistance only when it is exposed to light.
  • A photoresistor is a type of light-dependent resistor that varies its resistance values based on the light incident on it. 
  • These photoresistors tend to decrease their resistance values with an increase in the intensity of the incident light.
  • Photoresistors exhibit photoconductivity. 
  • These are less photo-sensitive devices compared to photodiodes and phototransistors. The Photoresistivity of a photoresistor varies with changes in ambient temperature.
  • These resistors are used as light sensors and the applications of LDR mainly include alarm clocks, street lights, light intensity meters, burglar alarm circuits.

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