The main parameters of resistors/resistors

Resistors/Main parameters of resistors
In the use of resistors, the parameters of resistors must be applied correctly. The performance parameters of resistors include nominal resistance and allowable deviation, rated power, maximum working voltage, resistance temperature coefficient, frequency characteristics and noise electromotive force, etc. For ordinary resistors, the most commonly used parameters are nominal resistance and allowable deviation, rated power.
⑴ Nominal resistance value and allowable deviation
Each resistor is produced in series and has a nominal resistance. For different nominal series, the actual value of the resistor is within the allowable error range of the nominal series. For example, the nominal value of a resistor in the E24 series is 1000 ohms, and the deviation of the E24 series resistor is 5%. The actual value of this resistor may be a value within the range of 950 to 1050 ohms. The specific resistance measured by the instrument is the actual value of this resistor.
Table 1-4 Appearance and characteristics of several fixed resistors

Pressure. Instruments, meters, etc. Circuits.
In circuits that require small resistance deviations, E48, E96, and E192 precision resistor series can be selected. In the use of resistors, resistors of different precisions are selected according to actual needs. Generally speaking, resistors with small errors have small temperature coefficients and high resistance stability.
The unit of resistance is ohm, represented by the symbol Ω. It is also commonly represented by units such as kilo-ohms (KΩ) and mega-ohms (MΩ). The conversion relationship between units is: 1MΩ＝1000KΩ＝1000000Ω
⑵ Rated power of resistors
In circuits, resistors are actually components that convert electrical energy into thermal energy, consuming electrical energy to increase their own temperature. The rated power of a resistor refers to the maximum power value that can be sustained by long-term continuous work under specified atmospheric pressure and specific temperature environmental conditions. The actual electrical power P consumed by a resistor is equal to the product of the voltage applied to the resistor and the current flowing through the resistor, that is, P＝UI. The rated power of resistors ranges from 0.05W to 500W in dozens of specifications. When using resistors, the rated power of the resistor should be 1.5 to 2 times greater than the actual power value of the resistor in the circuit.

Table 1-5 Naming methods for resistors and potentiometers

Figure 1-4 Graphical symbols of resistor rated power
In modern electronic devices, new resistors such as cement resistors and pinless sheet resistors are also commonly used.
Cement resistors are small in size and high in power, and are often used as step-down or shunt resistors in circuits.

There are two types of chip resistors, thick film chip resistors and thin film chip resistors. Thick film resistors are commonly used, such as the domestic RL11 series chip resistors. The characteristics of chip resistors are small size, light weight, good high-frequency characteristics, and no pins are installed by soldering. In addition, there are integrated resistors (row resistors).