Resistance: The resistance of a conductive body to current is called resistance, represented by the symbol R, in ohms, kiloohms, and megaohms, respectively represented by Ω, K Ω, and M Ω.

Naming method for resistor models: The model of domestically produced resistors consists of four parts (not applicable to sensitive resistors) ① main name ② material ③ classification ④ serial number

Classification of Resistors: ① Wirewound Resistors ② Thin Film Resistors: Carbon Film Resistors, Synthetic Carbon Film Resistors, Metal Film Resistors, Metal Oxide Film Resistors, Chemical Deposition Film Resistors, Glass Glazed Film Resistors, Metal Nitride Film Resistors ③ Solid Resistors ④ Sensitive Resistors: Varistors, Thermistors, Photosensitive Resistors, Force Sensitive Resistors, Gas Sensitive Resistors, and Humidity Sensitive Resistors.

Method for marking the resistance value of resistors:

1. Direct marking method: Use numbers and unit symbols to mark the resistance value on the surface of the resistor, and the allowable error is directly expressed as a percentage. If no deviation is indicated on the resistance, it is ± 20%.

2. Text symbol method: The nominal resistance value is represented by a regular combination of Arabic numerals and text symbols, and the allowable deviation is also represented by text symbols. The number before the symbol represents the integer resistance value, while the number after it represents the first decimal resistance value and the second decimal resistance value in sequence. Text symbols indicating allowable errors: DFGJKM. The allowable deviations are: ± 0.5% ± 1% ± 2% ± 5% ± 10% ± 20%

3. Digital method: A method of marking nominal values on resistors using three digit numbers. The number is from left to right, with the first and second digits being the significant value and the third digit being the exponent, which is the number of zeros, measured in euros. Deviation is usually represented by textual symbols.

4. Color coding method: Use different colored strips or dots to mark the nominal resistance value and allowable deviation on the surface of the resistor. Most foreign resistors use color coding method. Black-0, brown-1, red-2, orange 3, yellow-4, green-5, blue-6, purple-7, gray-8, white-9, gold - ± 5%, silver - ± 10%, colorless - ± 20%. When the resistance is four rings, the last ring must be gold or silver, with the first two digits being significant numbers, the third digit being the power, and the fourth digit being the deviation. When the resistance is five rings, the distance between the last ring and the front four rings is relatively large. The first three digits are significant digits, the fourth digit is the power, and the fifth digit is the deviation.

Identification of resistance value for SMT resistors: (On the surface of typical SMT resistors, numbers or letters are used to represent the resistance value. The resistance value method is as follows.)

The first and second digits represent the real number of resistance.

2. If the number starting from the third digit is 0, it represents several tens of ohms (between 10 and 99 ohms). Column: 100 represents a resistance of 10 ohms, and 990 represents a resistance of 99 ohms

3. If the number starting from the third digit is 1, it represents several hundred euros (between 100 and 999 euros). For example, 101 represents 100 euros, 151 represents 150 euros, and 951 represents 950 euros

4. If the number starting from the third digit is 2, it represents several thousand euros (between 1000 and 9999 euros). For example, 102 is 1K, 152 is 1.5K, and 992 is 9.9K

5. If the number starting from the third digit is 3, it represents tens of K (between 10K and 99K). For example, 103 represents 10K