The basic function of electronic components is to hinder the flow of electric current. The two more basic parameters to measure 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 basic unit, there are thousands of ohms 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., more than this larger value, the resistance The device will burn out. According to the different materials of the resistor, there are cement resistors (low production cost, high power, large thermal noise, insufficient resistance **, unstable work), carbon film resistors, metal film resistors (small size, stable operation, low noise , High precision) and metal oxide film resistance and so on. According to whether its resistance is variable or not, it can be divided into trimming resistor, adjustable resistor, potentiometer and so on.