The six functions of the resistance are current limiting, shunt, filtering of the resistance, voltage division, converting electrical energy into internal energy, and resistance bias. The resistance of a conductor to current is called the resistance of that conductor. Resistors (resistors, usually denoted by "R") are the most used components in all electronic circuits.

‌Classified by materials and processes ‌ :

‌Carbon film resistor: low cost, poor accuracy and stability, suitable for low precision circuits. ‌

Metal film resistor: high precision, good stability, suitable for high precision circuit.

Wire-wound resistor: high power, high precision, suitable for high-power circuit.

Cement resistor: high power, good heat dissipation, suitable for high power circuit. ‌

‌Classified by package ‌ :

·‌ Through hole insertion (THT) resistor: suitable for manual or semi-automatic production lines. ‌

·‌ Surface Mount (SMT) resistors: suitable for automated production, common in modern electronic equipment.

‌ Classified by use:

·‌ Universal type: suitable for general technical requirements of the circuit. ‌

·‌ Thermistor: The resistance varies with temperature. It is used for temperature measurement and protection. ‌

·‌  Varistor: Resistance varies with voltage. Used for over voltage protection.

·‌ Photoresistor: resistance varies with the light intensity, used for optical switching and measurement.

·‌ Gas resistor: resistance changes with gas concentration. Used for gas detection.

‌ Categorized by function:

·‌ Fixed resistor: The resistance is fixed and is used when a stable resistance is required.

·‌ Adjustable resistor (potentiometer): The resistance value is adjustable, used in the need to adjust the circuit parameters.

·‌ Divider: Used to reduce the voltage in a circuit.

·‌ Current limiting resistor: Used to limit the current in a circuit.

·‌ Sampling resistor: Used for current detection and signal sampling.

Six Functions of Resistance:

1, current limiting: In order to make the current through the electrical appliance does not exceed the rated value or the specified value required for actual work to ensure the normal operation of the electrical appliance, usually a variable resistor can be connected in series in the circuit. When the size of this resistance is changed, the size of the current also changes. We call this kind of resistance that can limit the size of the current current-limiting.

2, shunt: when several electrical appliances with different rated current need to be connected at the same time on the dry road of the circuit, a resistor can be connected in parallel at both ends of the electrical appliance with smaller rated current, and the role of this resistor is shunt.

3, voltage division: general electrical appliances are marked with the rated voltage value, if the power is higher than the rated voltage of the electrical appliance, you can not directly connect the electrical appliance to the power supply, in this case, the electrical appliance can be connected to a suitable resistance value resistance, so that it can share a part of the voltage, the electrical appliance can work under the rated voltage. We call such a resistor a partial voltage resistor.

4, convert electrical energy into internal energy: When the current passes through the resistor, it will convert all (or part) of the electrical energy into internal energy. Electrical appliances used to convert electrical energy into internal energy are called electric heaters. Such as electric iron, electric stove, rice cooker, heater and so on.

5, resistance bias action: the bias circuit often has a number of components, of which there is an important resistance, often to adjust the resistance value, so that the collector current in the design specification. The resistance to be adjusted is the bias resistance.

6, the filtering effect of the resistance: the filtering effect of the resistance is generally composed of a RC filter circuit and a capacitor, which can be divided into low-pass and high-pass circuits.