What is a resistor?
The resistance of resistor conductor to current is called resistance, which is expressed by symbol R, and the unit is ohm （Ω）, kilo ohm Ω ( kΩ ), meg ohm ( MΩ ).
Resistor is one of the basic components in electrical and electronic equipment, which is mainly used to control and regulate the current and voltage in the circuit, or used as a load to consume electrical energy. There are many kinds of resistors, which are usually divided into three categories, namely, fixed resistors, variable resistors and special resistors. In electronic products, fixed resistors are the most widely used.
First,The classification of fixed resistors
1. According to material
(1) Resistors such as wirewound resistors mainly include general wire wound resistors, precision wire wound resistors, high-power wound resistors and high frequency wire wound resistors.
(2) Thin film resistors include carbon film resistors, synthetic carbon film resistors, metal film resistors, metal oxide film resistors, chemical deposition film resistors, glass glaze resistors and metal nitride film resistors.
(3) Solid resistor. These resistors include inorganic synthetic solid carbon resistors and organic solid carbon resistors.
2. According to the power, there are 1 / 8W, 1 / 4W, 1 / 2W, 1W and other color ring carbon film resistors, they are the most used in electronic products and electronic production. In some microproducts, a 1 / 16W resistor is also used, which is much smaller. And then there is the miniature sheet resistor.
Second, the main characteristic parameters
( 1 ) nominal resistance refers to the resistance of the resistor surface.
( 2 ) The percentage of the difference between the nominal resistance of the allowable deviation and the actual resistance and the ratio of the nominal resistance is called the permissible deviation, which represents the accuracy of the resistor.
( 3 ) Rated power refers to the allowable dissipation of the resistor for a long time under the conditions of normal atmospheric pressure of 90 ~ 106. 6 kPa and ambient temperature of -55 ~ + 70C the maximum power.
( 4 ) Rated voltage refers to the voltage converted from resistance and rated power.
( 5 ) Maximum working voltage is the maximum continuous operating voltage that is allowed to be added to both ends of the resistor. When working at low pressure, the maximum operating voltage is low.
( 6 ) The temperature coefficient is the relative change of the resistance value caused by the change of temperature per 1℃. The smaller the temperature coefficient, the better the stability of the resistance. The positive temperature coefficient increases with the increase of temperature, and vice versa.