Current flowing through a conductor coiled around an iron bar produces a(n)?

• A. Inductor
• B. Capacitor
• C. Resistor
• D. Electromagnet

Answer: (D)

The key idea is that magnetic fields are created by electric current, and a coil around a ferromagnetic core concentrates that field. When current passes through the coil, it induces a magnetic field, and the iron bar provides a low-reluctance path that magnetizes and concentrates this field, turning the assembly into a magnet whose strength is controlled by the current. That is what makes it an electromagnet.

A capacitor stores energy in an electric field, not a magnetic field. A resistor converts electrical energy to heat with no magnetic behavior in its defining function. An inductor is a coil that stores energy in a magnetic field, but the presence of the iron core that produces a noticeable magnetization distinguishes it as an electromagnet.