When coils are wrapped around an iron core, what increases?

• A. Efficiency
• B. Magnetic Leakage
• C. Heat
• D. Capacitance

Answer: (A)

When you wrap coils around an iron core, the path for the magnetic field becomes highly permeable, so the magnetic flux for a given current increases and links the windings more effectively. This lowers magnetic reluctance and reduces flux leakage, meaning more of the input energy is transferred to the output rather than wasted in stray fields. In devices like transformers, that stronger, better-confined flux improves energy transfer efficiency. Capacitance isn’t meaningfully affected by the core in this context, and while core losses (like hysteresis and eddy currents) can add heat, the overall effect of the iron core in this setup is to raise efficiency through improved flux linkage.