ARRL Technician Practice Exam

Which component is combined with an inductor to make a tuned circuit?

1. Resistor

2. Capacitor

3. Transformer

4. LED

The correct answer is: Capacitor

A tuned circuit, also known as a resonant circuit, typically consists of an inductor and a capacitor working together to resonate at a specific frequency. When the inductor and the capacitor are combined, they form a parallel or series resonant circuit that can select or amplify signals at that particular frequency while rejecting others. This property is essential in various applications such as radio transmitters and receivers, where tuning to specific frequencies is necessary for proper operation. The other components listed, such as a resistor, transformer, and LED, do not create a tuned circuit in conjunction with an inductor. A resistor can be part of a circuit but does not help in tuning. A transformer functions primarily to change voltage levels and does not create resonance. An LED is a light-emitting diode, which serves a different purpose entirely and cannot create a resonant effect when paired with an inductor. Thus, the combination of an inductor and a capacitor is fundamental for the operation of tuned circuits.