Current-limiting resistor



A Resistor limits the amount of Current running through a Circuit. To explain how a current limiting resistor works, the most basic circuit involving just three Components will be used as an example. Take a power source, in this case a 3 Volt Battery, and a load (battery. A load is any component that requires power to function. In this example, the LED consumes .018 amperes (A) at 2 volts. Since our input power (5 V) is higher than the power usage of our device (2 V), a current limiting resistor has to be used. The resistance value is obtained using ohm's law: V = IR, where V = (Vsource - Vload), I = .018, and R is the resistance value. 3-2 = .018*R. 1/.018 = R. R = 55 ohms. Using a resistor of value 55 ohms in series with the LED will allow safe operation of the LED. Without the resistor, the LED will most likely burn out.