The more basic electronic component is to block the flow of electricity. The two basic parameters used to measure a resistor are resistance and power. The resistance value is used to indicate the magnitude of the resistance to the current obstruction, expressed in ohms. In addition to the basic units, there are kilohm and megohm. Power is used to represent the resistor can withstand the larger current, expressed in watts, there are 1/16W, 1/8W, 1/4W, 1/2W, 1W, 2W and so on, beyond this larger value, the resistor will burn out. According to the production material of the resistor, there are cement resistance (low production cost, large power, large thermal noise, resistance value is not perfect, unstable work), carbon film resistance, metal film resistance (small volume, stable work, small noise, high precision) and metal oxide film resistance and so on. According to its variable resistance value can be divided into fine tuning resistance, adjustable resistance, potentiometer and so on.