What is a resistor. Why do you need to add a resistor to the LED lamp bead, and what effect does the resistor have on the LED lamp bead? So the next thing to talk about is what is the effect of resistance on LED lamp beads. simply put. Resistance refers to the resistance that current encounters in a circuit, or the ability of an object to block the current. The LED lamp beads and the power supply voltage are not necessarily equal. Generally, the power supply voltage will be slightly higher than the LED lamp bead voltage. At this time, it is necessary to add a series resistor to reduce the voltage and limit the current to maintain normal operation and prevent the LED lamp bead from burning when it is working. So how big is the resistor? 1. Low power red and yellow, its resistance = voltage / current = 1.8/0.02 = 90Ω. 2. Low-power blue-green, its resistance = voltage / current = 3.2/0.02 = 160Ω. 3. High-power red and yellow, its resistance=voltage/current=2.2/0.35=6Ω. 4. For high-power blue-green, its resistance=voltage/current=3.4/0.35=10Ω. Resistance is a physical quantity. In physics, it represents the size of the resistance of a conductor to current. Its English name is resistance, usually abbreviated as R. It is a basic property of the conductor, which is related to the size, material and temperature of the conductor. The greater the resistance of the conductor, the greater the resistance of the conductor to the current flow. Different conductors generally have different resistances. The basic unit of resistance is the ohm, represented by the Greek letter "Ω". Ohm's law states that the relationship between voltage, current and resistance is I=U/R, that is, R=U/I. The resistance value of a resistive element is generally related to temperature, material, length, and cross-sectional area. The physical quantity that measures the resistance to temperature is the temperature coefficient, which is defined as the percentage of the resistance value that changes when the temperature increases by 1°C. The main physical feature of a resistor is to convert electrical energy into thermal energy. It can also be said that it is an energy-consuming element, and the current passes through it to generate internal energy. Resistors usually play the role of voltage divider and current shunt in the circuit. For signals, both AC and DC signals can pass through resistors.