Which type of transformer core assembly offers low resistance to magnetic lines of force?

• A. Iron
• B. Nickel
• C. Copper
• D. Aluminum

Answer: (A)

The key idea is that a transformer core should provide a path for magnetic flux with very low reluctance, meaning high magnetic permeability. Iron fits this requirement well: it lets magnetic lines of force pass through easily, so the magnetic circuit has minimal opposition and the required magnetizing current is reduced. When used in laminated form, iron also minimizes eddy currents, keeping losses low while maintaining a strong, low-reluctance path for the flux.

Copper and aluminum are great electrical conductors, but their magnetic permeability is very low, so they offer a high reluctance path and would not channel the magnetic flux efficiently. Nickel is ferromagnetic, but among the given options, iron provides the most favorable combination of permeability and practical core properties for low-reluctance flux guidance.