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JDPD8W180400K

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9

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原 价：

10 元

活动价：

9 元

I. Basic Principles of Resistance

The resistance of a resistor is a physical quantity that measures its ability to oppose the flow of electric current, with the unit being the ohm (Ω). According to Ohm’s law, the voltage (V) across a resistor is directly proportional to the current (I) passing through it, and the proportionality constant is the resistor’s resistance (R), expressed by the formula:
V = I × R
The resistance of a resistor is determined by its material, dimensions, and structure. The resistivity (ρ) of the resistor material is an intrinsic property, while the resistor’s geometric dimensions—such as length and cross-sectional area—are specified by the following formula: R = ρ × (L/A) To calculate, where L is the length of the resistor and A is the cross-sectional area.

II. Classification of Resistors

By material classification
Carbon film resistor : Using carbon powder as the primary material, it offers low cost and good stability, but relatively lower precision, making it commonly used in standard circuits.
Metal film resistor : Using metal oxides as the material, it offers high precision and excellent stability, making it suitable for high-precision circuits.
Wire-wound resistor : Wound from metal wire, it offers a wide range of resistance values and high power-handling capability, but its bulky size makes it suitable primarily for high-power circuits.
Ceramic resistor : Based on ceramic materials, it exhibits excellent heat resistance and thermal stability, making it suitable for high-temperature environments.
Thin-film resistor : Thin films are formed on substrates via vacuum deposition, offering high precision and compact size, and are commonly used in precision circuits.
By Functionality
Fixed resistor : Its resistance value is fixed and does not change; it is the most common type of resistor.
Variable resistor : Resistance values can be adjusted mechanically or electrically, such as with potentiometers and rheostats, and are commonly used for signal conditioning and impedance matching.
Special-function resistor For example, thermistors (whose resistance varies with temperature), photoresistors (whose resistance varies with light intensity), and varistors (whose resistance varies with voltage) are used in sensors and protective circuits.