What factor increases the strength of an electromagnet?

• A. A larger air gap between the coil and the core
• B. More coil turns
• C. A thicker insulating layer around the wire
• D. A lower input voltage

Answer: (B)

The strength of an electromagnet comes from ampere-turns—the product of how many times the wire is wound and how much current flows. More coil turns means more loops for the same current, so the magnetic field lines add up and the core concentrates a stronger flux. In other words, increasing the number of turns directly increases the magnetic field produced.

Why the other factors don’t boost strength as effectively: a larger air gap increases reluctance in the magnetic path, which weakens the flux, since the magnetic circuit becomes less efficient. A thicker insulating layer mainly affects resistance and heat, not the amount of magnetic flux produced. A lower input voltage typically reduces the current, which lowers the magnetic field. So adding more turns is the best way to strengthen the electromagnet.