What component is used to limit the current in a light-emitting diode (LED)?

The component used to limit the current in a light-emitting diode (LED) is a current limiting resistor. LEDs are sensitive devices that can be easily damaged if subjected to excessive current. When a forward voltage is applied to an LED, it allows current to flow, producing light. However, without proper current control, the LED could draw too much current and overheat, leading to failure.

The current limiting resistor is placed in series with the LED in the circuit. Its primary role is to provide resistance to the flow of current, thereby ensuring that the current remains below the maximum rating for the LED. By calculating the appropriate resistance value using Ohm's law, you can set the desired current flowing through the LED, which not only protects it but also ensures it operates efficiently in its intended application.

In comparison, other components listed, like a current transformer, voltage regulator, or capacitor, serve different purposes in circuits, and are not suitable for directly limiting the current through an LED. A current transformer is designed for monitoring current in AC circuits, a voltage regulator manages voltage levels, and a capacitor stores electrical energy. Therefore, the current limiting resistor is the correct and appropriate choice for managing the current in LED applications.