Which type of coil is better for magnetic lines of force?

• A. Soft-iron coil
• B. Air coil
• C. Wood coil
• D. Plastic coil

Answer: (A)

The better choice for magnetic lines of force is a soft-iron coil because soft iron has high magnetic permeability, meaning it can easily become magnetized and support the establishment of strong magnetic fields. When an electric current flows through a coil made of soft iron, the iron core enhances the magnetic field produced by the coil, effectively concentrating and directing the magnetic lines of force. This property makes soft-iron coils highly effective in applications such as transformers and electromagnets, where a strong and concentrated magnetic field is required.

In contrast, air coils do not have a ferromagnetic core, so the magnetic field generated is not as effective or strong compared to one with a ferromagnetic material. Wood and plastic coils, being non-magnetic materials, do not contribute to the establishment of magnetic lines of force at all, leading to much weaker magnetic fields. Therefore, soft-iron coils are the superior choice due to their ability to significantly enhance magnetic field strength.