Much stronger ________ fields are obtained if the wire is wound into a coil with many turns of wire.

Much stronger ________ fields are obtained if the wire is wound into a coil with many turns of wire.

• A. Electric
• B. Magnetic
• C. Electromotive
• D. Resistance

Answer: (B)

Magnetic field strength increases when the wire is wound into a coil with more turns. Each loop of current generates a magnetic field, and those fields add together in the same direction inside the coil. With more turns, the overall field becomes stronger for the same current. In a long solenoid, the field is roughly B ≈ μ0 n I, with n being turns per length, so more turns per length (or more total turns for a given length) increases B. This is the idea behind electromagnets and inductors—the magnetomotive force NI (ampere-turns) drives the magnetic field. Electric fields and electromotive fields aren’t strengthened by simply adding turns, and increasing turns mainly raises resistance due to more wire, not the magnetic field.

Magnetic field strength increases when the wire is wound into a coil with more turns. Each loop of current generates a magnetic field, and those fields add together in the same direction inside the coil. With more turns, the overall field becomes stronger for the same current. In a long solenoid, the field is roughly B ≈ μ0 n I, with n being turns per length, so more turns per length (or more total turns for a given length) increases B. This is the idea behind electromagnets and inductors—the magnetomotive force NI (ampere-turns) drives the magnetic field. Electric fields and electromotive fields aren’t strengthened by simply adding turns, and increasing turns mainly raises resistance due to more wire, not the magnetic field.