1、 Resistor (R)

Resistance, for short, refers to the element with certain technical performance that plays the role of resistance in the circuit. It can be used to adjust the current and voltage in the circuit, or as a load in the circuit.

1. Parameters of resistance:

a. Resistance: refers to the value of resistance. 0 Ω - several hundred m Ω

b. Dissipative power: refers to the maximum power that the resistor can bear (consume) during long-term operation.

2. Material of resistance:

The commonly used materials for resistance include carbon film, metal film, metal oxide film, wire wound, cement (ceramic) wire wound semiconductor and so on.

3. Type of resistance:

① Fixed resistance: refers to the resistance with fixed resistance value

② Trimming resistance: refers to the resistance whose resistance value can be adjusted

③ Adjustable resistance: commonly known as potentiometer, it refers to the resistance with continuously adjustable resistance value

④ Thermistor: refers to the resistance whose value changes with temperature

a. Positive temperature coefficient thermistor: refers to the resistance (PTC) whose resistance value increases with the increase of temperature

b. Negative temperature coefficient thermistor: refers to the resistance whose value decreases with the increase of temperature

⑤ Varistor: refers to the resistance whose value changes with the change of voltage.

⑥ Humidity sensitive resistance: refers to the resistance whose value changes with temperature

⑦ Photosensitive resistance: refers to the resistance whose value changes with temperature

⑧ Power representation of resistance: generally, high-power (above 3W) resistors are marked with their power values on the resistance shell, such as 3W, 5W, 7W, 10W, 20W, 30W, etc., while low-power (below 3W) is partially marked with power (such as 3W, 2W, 1W, etc.), and those without power are mostly low-power resistors below 1W. For practical use, The resistance with high power can be used to replace the resistance with low power. On the contrary, it cannot be replaced. If the resistance power is not known, the resistance with the same or slightly larger volume can be used in practical application.