Power winding resistance is a resistive material, a certain structure can limit the current in the circuit by acting from the two ends of electronic components. Can not change the resistance called a fixed resistor. Resistance variable called potentiometer or variable resistor. Ideal resistor is linear, that is the instantaneous current through the resistor is proportional to the instantaneous voltage applied. Some special resistors such as thermistors, varistors and sensitive element, the voltage and current relationship is nonlinear. Resistor is the largest number of the application of the electronic circuit component, usually the formation of different power and resistance range for circuit designers choice. Resistor in the circuit is mainly used to adjust and stabilize the current and voltage, and a voltage divider can be used as shunt, also can make the load matching circuit. According to requirements of the circuit can be used for negative feedback amplification circuit or positive feedback, the voltage - current converter, the input voltage or overload current protection device, the RC circuit can be formed as an oscillation, filter, bypass, differentiation, integration, and the time constant components. Power Film Resistors small role is typically packaged in plastic housing of the carbon film, and the power resistance of the resistor wire wound resistor is typically through the large resistance of the metal wire around the heart and made in a porcelain . If the resistance value of a resistor close to zero ohms (for example, the large cross-section between two wires), the resistor of the current does not hinder, this resistor series circuit is short-circuited, the current infinity. If a resistor having infinite or a large resistor is connected in series to the resistor can be seen as an open circuit, the current is zero. Commonly used in industry resistor between the two extremes, it has a certain resistance through a constant current, but the current is not as large as a short circuit. Limiting resistor works like two large diameter pipes connected to the small-diameter pipe between the water flow restriction effect. Resistance, English name resistance, often abbreviated to R, which is one of the basic properties of the conductor, the conductor size, material, temperature. Ohm's Law says, I = V / R, then R = V / I, the basic unit is ohm resistor, with the Greek letter "Ω" means, with this definition: conductor plus one volt, the resulting current of one ampere corresponding to the resistance value. The main function is to discourage resistance current flow. In fact, the "resistance" that is a property, and are usually referred to in the electronics resistor means is a resistor element. Master of the apprentice said: "find a 100 ohm resistor to!", Refers to a "resistance" as the 100 ohm resistor, Ohm often referred to as Europe. Represents a common resistor unit also kilohms (kΩ), Meg (MΩ).