The resistance of a conductor to current flow is called the resistance of the conductor. Substances with low resistance are called electrical conductors, or conductors for short. Substances with high electrical resistance are called electrical insulators, or insulators for short.

In physics, resistance is used to represent the size of a conductor's resistance to current flow. The greater the resistance of the conductor, the greater the resistance of the conductor to the current flow. Different conductors generally have different resistances, and resistance is a property of the conductor itself.

The resistance of a conductor is usually represented by the letter R. The unit of resistance is ohm (ohm), abbreviated as ohm, and the symbol is Ω (Greek letter, transliterated into pinyin and read as ōu mì gǎ ). The larger units are kiloohms (kΩ) and megohms (MΩ) (mega=million, or 1 million).

Resistor for short (Resistor, usually represented by "R") is the most used component in all electronic circuits. The main physical feature of a resistor is to convert electrical energy into thermal energy. It can also be said that it is an energy-consuming element, and the current passes through it to generate internal energy. Resistors usually play the role of voltage divider and current divider in the circuit. For signals, both AC and DC signals can pass through the resistor.

KΩ (kiloohm), MΩ (megaohm), their conversion relationship is:

1TΩ=1000GΩ 1GΩ=1000MΩ 1MΩ=1000000Ω 1KΩ=1000Ω

The standard method of resistance value of resistor is usually color ring method and digital method. The color ring method is more common on general resistors. Since the resistance in the mobile phone circuit is generally relatively small, it is rarely marked with a resistance value. Even if there is, the digital method is generally used, that is:

10^1——Represents 10Ω resistance; 10^2——Represents 100Ω resistance; 10^3——Represents 1KΩ resistance; 10^4——Represents 10KΩ resistance; 10^6——Represents 1MΩ resistance; 10^7 - represents a resistance of 10MΩ.

If a resistor is marked 22*10^3, then the resistor is 22KΩ.

Digital method

The nominal value of the component is expressed as a three-digit number. From left to right, the first two digits represent significant digits, and the third digit represents 10n (n=0～8). It is a special case when n=9, which means 10^(-1). 103 for a plastic resistor means 10*10^3=10k. Chip resistors are usually marked with a digital method, such as 512 for 5.1kΩ. The number 479 on the capacitor is 47*10^(-1)=4.7pF. A resistor with a sign of 0 or 000 indicates a jumper with a resistance value of 0Ω. When the digital method is used for marking, the unit of resistance is ohm, the unit of capacitance is pF, and the inductance is generally not marked with digital.

The electrical performance indicators of resistors usually include nominal resistance, error and rated power.

It forms some functional circuits together with other components, such as RC circuits.

A resistor is a linear element. It is said that it is a linear element because it is found through experiments that under certain conditions, the current flowing through a resistor is proportional to the voltage across the resistor - that is, it conforms to Ohm's law: I=U/R

Common carbon film resistors or metal film resistors can be simulated by linear resistors when the temperature is constant and the voltage and current values are limited within the rated conditions. If the voltage or current value exceeds the specified value, the resistor will overheat and not obey Ohm's law, or even burn out. There are many types of resistors, usually divided into carbon film resistors, metal resistors, wirewound resistors, etc.: it also includes fixed resistors and variable resistors, photoresistors, varistors, thermistors, etc.

Generally speaking, it is easy to judge the quality of the resistance by using a multimeter: adjust the multimeter to the appropriate gear of the electric resistance, and place the two test leads of the multimeter at the two ends of the resistance, and then the resistance of the resistance can be read from the multimeter. resistance. It should be noted that when testing the resistance, the metal part of the test lead should not be touched by hand. But in actual electrical maintenance, resistance damage rarely occurs. The main thing to pay attention to is whether the resistance is soldered or unsoldered.

Effect:

The main function is to hinder the flow of current, and it is used in current limiting, shunt, step-down, voltage division, load and capacitor cooperation as filter and resistance matching, etc. The functions in digital circuits include pull-up resistors and pull-down resistors.