Good product, good way # Resistors

The terminal voltage and current have a definite function relationship, and the two-terminal device that reflects the ability of electric energy to be converted into other forms is represented by the letter R, and the unit is ohm Ω. Actual devices such as light bulbs, heating wires, resistors, etc. can be represented as resistor elements.

### Definitions and materials

Resistors are commonly referred to as resistors in daily life. It is a current-limiting component. After the resistor is connected to the circuit, the resistance of the resistor is fixed, usually two pins, which can limit the current flowing through the branch connected to it. The resistance that cannot be changed is called a fixed resistor. Variable resistance is called a potentiometer or variable resistor. The ideal resistor is linear, that is, the instantaneous current through the resistor is proportional to the applied instantaneous voltage. Variable resistor for voltage division. On the exposed resistor body, one or two movable metal contacts are pressed tightly. The position of the contact determines the resistance between either end of the resistor and the contact.

The terminal voltage and current have a definite function relationship, and the two-terminal device that reflects the ability of electric energy to be converted into other forms is represented by the letter R, and the unit is ohm Ω. Actual devices such as light bulbs, heating wires, resistors, etc. can be represented as resistor elements.

The resistance value of a resistance element is generally related to temperature, material, length, and cross-sectional area. The physical quantity that measures the resistance affected by temperature is the temperature coefficient, which is defined as the percentage change in resistance value when the temperature increases by 1 ° C. The main physical characteristic of a resistor is to change electrical energy into thermal energy. It can also be said that it is an energy-consuming element, and current passes through it to generate internal energy. The resistor usually plays the role of voltage division and current distribution in the circuit. For signals, both AC and DC signals can pass through resistors.

### Classification

Classified by volt-ampere characteristics
For most conductors, at a certain temperature, its resistance remains almost constant and becomes a certain value. This type of resistance is called linear resistance. The resistance of some materials changes significantly with current (or voltage), and its volt-ampere characteristic is a curve. This type of resistance is called a non-linear resistance. Non-linear resistance under a given voltage (or current), the ratio of voltage to current is the static resistance at this operating point, and the slope on the volt-ampere characteristic curve is the dynamic resistance. The way to express the non-linear resistance characteristics is more complicated, but these non-linear relationships have been widely used in electronic circuits.

Classified by material
a. Wire-wound resistors are made of resistance wires wound into resistors. High-resistance alloy wires are wound on the insulating skeleton, and the outside is coated with a heat-resistant glaze insulating layer or insulating paint. Wirewound resistors have a low temperature coefficient, high resistance accuracy, good stability, heat resistance and corrosion resistance. They are mainly used as precision high-power resistors. The disadvantages are poor high-frequency performance and large time constants.

b. Carbon composite resistors are made of carbon and synthetic plastic.

c. The carbon film resistor is made by coating a layer of carbon on the porcelain tube, and the crystalline carbon is deposited on the ceramic rod skeleton. Carbon film resistors are the most widely used resistors at low cost, stable performance, wide resistance range, low temperature coefficient and voltage coefficient.

d. The metal film resistor is formed by plating a layer of metal on a porcelain tube, and the alloy material is evaporated on the surface of the ceramic rod skeleton by a vacuum evaporation method.
Metal film resistors have higher accuracy than carbon film resistors, good stability, low noise, and low temperature coefficient. It is widely used in instrumentation and communication equipment.

e. The metal oxide film resistor is plated with a layer of tin oxide on the porcelain tube, and a layer of metal oxide is deposited on the insulating rod. Because it is an oxide itself, it is stable at high temperatures, resistant to heat and shock, and has a strong load capacity. According to the purpose, there are general, precision, high frequency, high voltage, high resistance, high power, and resistance networks.

Special resistor
1. Fuse resistor: It is also called a fuse resistor. Under normal circumstances, it plays the dual role of resistance and fuse. When the circuit fails and its power exceeds the rated power, it will blow like a fuse to disconnect the connection circuit. Fuse resistors generally have low resistance values ​​(0.33Ω to 10KΩ) and low power.

2. Sensitive resistor: It means that its resistance value is sensitive to a certain physical quantity (such as temperature, humidity, light, voltage, mechanical force, and gas concentration, etc.). When these physical quantities change, the resistance of the sensitive resistor is Will change with the change of physical quantity, showing different resistance values. According to the sensitivity to different physical quantities, the sensitive resistors can be divided into thermal sensitive, humidity sensitive, light sensitive, pressure sensitive, force sensitive, magnetic and gas sensitive and other types of sensitive resistors. The materials used for sensitive resistors are almost all semiconductor materials. This type of resistor is also called a semiconductor resistor.

The resistance of the thermistor changes with temperature. The resistance to temperature rise is a negative temperature coefficient (NTC) thermistor. The most commonly used are negative temperature coefficient thermistors, which can be divided into ordinary negative temperature coefficient thermistors; voltage regulator negative temperature coefficient thermistors; temperature measuring negative temperature coefficient thermistors and so on. Photoresistor is the resistance of the resistance changes with the intensity of the incident light.
When the incident light increases, the photoresistor decreases, and when the incident light decreases, the resistance value increases.

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