The basic function of electronic components is to hinder the flow of current. The two more basic parameters for measuring resistors are resistance and power. The resistance value is used to indicate the size of the resistance of the resistor to the current, expressed in ohms. In addition to the base unit, there are kiloohms and megohms. Power is used to indicate the larger current that the resistor can withstand. It is expressed in watts. There are 1/16W, 1/8W, 1/4W, 1/2W, 1W, 2W, etc., beyond this larger value, the resistance device will burn out. According to the different materials of resistors, there are cement resistors (low production cost, high power, high thermal noise, insufficient resistance, unstable work), carbon film resistors, metal film resistors (small size, stable operation, low noise) , high precision) and metal oxide film resistors and so on. According to whether its resistance is variable, it can be divided into fine-tuning resistors, adjustable resistors, potentiometers, etc.