Which coil shape is identified as producing a stronger magnetic field compared to a flat coil?

Which coil shape is identified as producing a stronger magnetic field compared to a flat coil?

• A. Spiral
• B. Circular
• C. Rectangular
• D. Helical

Answer: (A)

The key idea is how many ampere-turns you have in a given space. A spiral coil winds wire many times within the same planar footprint, packing more turns into the area than a flat single-turn coil. Each loop contributes to the axial magnetic field, and their fields add up because the turns are closely spaced and share the same axis. So, for the same current, a planar spiral delivers more ampere-turns in the center than a flat coil with only one or few turns, producing a stronger magnetic field. The other shapes either have fewer turns in the same area (like a single circular or rectangular loop) or are arranged differently (a helical/solenoid), but the spiral specifically achieves a higher field than a flat coil through higher turn density in the plane.

The key idea is how many ampere-turns you have in a given space. A spiral coil winds wire many times within the same planar footprint, packing more turns into the area than a flat single-turn coil. Each loop contributes to the axial magnetic field, and their fields add up because the turns are closely spaced and share the same axis. So, for the same current, a planar spiral delivers more ampere-turns in the center than a flat coil with only one or few turns, producing a stronger magnetic field. The other shapes either have fewer turns in the same area (like a single circular or rectangular loop) or are arranged differently (a helical/solenoid), but the spiral specifically achieves a higher field than a flat coil through higher turn density in the plane.