ARRL Technician Practice Exam

What electrical component is usually composed of a coil of wire?

1. Capacitor

2. Resistor

3. Transformer

4. Inductor

The correct answer is: Inductor

An inductor is the electrical component that is primarily composed of a coil of wire. The fundamental operation of an inductor is based on the principle of electromagnetic induction, which involves the generation of magnetic fields around the coil when an electrical current flows through it. This characteristic allows inductors to store energy in the magnetic field and also to resist changes in current. When current passes through the wire coil, it creates a magnetic field that extends outward from the coil. This quality is integral to various applications in circuits, including filtering, energy storage for power applications, and tuning in radio frequency devices. The other options, such as capacitors and resistors, have their distinct functions and forms. A capacitor consists of two conductive plates separated by an insulating material and is used to store electrical charge. A resistor is a passive component that restricts the flow of current in a circuit, typically made from materials that have a specific resistance. A transformer, while it may have coils of wire, is a more complex device composed of at least two inductively coupled coils and is used to transfer electrical energy between circuits through electromagnetic induction.