Increasing the number of loops in a coil will increase the ? of the magnetic field.

• A. Current
• B. Resistance
• C. Size
• D. Strength

Answer: (D)

Increasing the number of loops in a coil boosts the magnetic field strength because the field inside a coil depends on the total ampere-turns, which is the current times the number of turns. In a long solenoid, B is proportional to N/L times I (or simply to NI for a fixed length), so adding more turns while keeping the current and length constant increases the field strength. The other ideas don’t directly set the field: current is determined by the source, not by simply adding loops, and the coil’s size doesn’t alone determine the field—more turns produce more magnetizing effect, i.e., a stronger field.