Some performance ratings of resistors are called its parameters. There are three main parameters of resistance: nominal resistance value, error and rated power.
1. Nominal resistance value and error
The nominal resistance value refers to the resistance value marked on the surface of the resistor. The deviation between the actual resistance value and the nominal resistance value is its error. The error range of resistors is generally divided into soil 5%, soil 10%, and soil 20%.
2. Rated power
Rated power is another main parameter of the resistor, expressed by W. The rated power depends on the structure, size and material.
The nominal series values of domestic resistor rated power are divided into 1/16, 1/8, 1/4, 1/2, 1, 2, 5, 10W and so on. The ones larger than 5W are directly indicated by numbers.
The unmarked in the circuit diagram indicates that the power consumption of this resistor in operation is very small, so it is unnecessary to consider.
The rated power of a resistor is closely related to its volume. The larger the rated power, the larger the volume. The rated power value of the resistor can be roughly judged from the volume of the resistor, which is very helpful to identify the resistor without the power label (such as the color ring resistor).
In addition, the rated power of metal film resistors and carbon film resistors of the same volume is one grade higher than the latter.