how does an led work in a circuit
LED circuit The simplest circuit to drive an LED consists of a voltage source and two components connected in series: a current limiting resistor, sometimes called the ballast resistor, and an LED. Optionally, a switch may be introduced to open and close the circuit. Although simple, this circuit is not the most energy efficient circuit to drive an LED, since energy is lost in the resistor. More complicated circuits improve the energy efficiency.