A coil that has a soft iron core and that acts as a magnet when an electric current is in the coil (solenoid with ferromagnetic core)

• A. Solenoid
• B. Electromagnet
• C. Inductor
• D. Magnetic coil

Answer: (B)

When current flows through a coil, it creates a magnetic field. If that coil has a soft iron core, the magnetic domains in the iron align with the field and the core greatly strengthens and concentrates the magnetism. The result is a coil that behaves like a magnet with distinct north and south poles while current is on, which is the hallmark of an electromagnet. The iron core is what makes it much stronger than a simple coil, and why this setup is specifically called an electromagnet.

A solenoid is just the coil shape, and without a ferromagnetic core it doesn’t become as strong a magnet (though it still produces a field). An inductor is focused on storing energy in the magnetic field and opposing changes in current, not on acting as a switchable magnet with poles. Magnetic coil is a vague label that doesn’t specify the device’s magnetic, switchable behavior.