Induction will be maximized and higher voltages obtained when the two coils are placed around which component?

• A. Iron Core
• B. Air Gap
• C. Copper Ring
• D. Plastic Core

Answer: (A)

Induction between two coils is maximized when the magnetic path linking the coils has very low reluctance, so the flux produced by the primary can be concentrated and shared by the secondary. Wrapping both coils around a material with high magnetic permeability—an iron core—greatly lowers the magnetic reluctance of the path the flux follows. With the core, the flux through the windings becomes larger for a given driving current, and changes in that flux induce a stronger voltage in the secondary (Faraday’s law). An iron core also helps keep the magnetic flux from leaking into surrounding space, improving coupling between the coils. In contrast, an air gap, a copper ring, or a plastic core offers much higher reluctance or poorer magnetic behavior, leading to weaker induction and lower voltages. Therefore, placing the coils around an iron core yields the greatest induction and highest voltages.