The eddy currents in a transformer are reduced by using

The correct answer is Option (4) → a laminated core.

Eddy currents are induced in the iron core itself by the changing flux, and heat the core. Making the core of thin iron sheets (laminations) insulated from each other breaks up the large current loops: each loop is confined to a thin sheet, the path resistance is high and the eddy currents become small.

Why the other options are incorrect

• Option (1) the primary and secondary windings one over the other. — Incorrect. Winding the coils one over the other reduces the flux leakage between primary and secondary, not eddy currents.

• Option (2) a material which has a low hysteresis loss. — Incorrect. A material with low hysteresis loss reduces the hysteresis loss in the core, a different energy loss.

• Option (3) a thick wire. — Incorrect. Thick wire lowers the resistance of the windings and so the \( I^{2}R \) (copper) loss in the coils, not eddy currents in the core.

Note: A similar question was also asked in CUET (UG) 2023 on 09-06-2023 (Slot 3).

NCERT (2026-27):
Transformers – “… (iii) Eddy currents: The alternating magnetic flux induces eddy currents in the iron core and causes heating. The effect is reduced by using a laminated core.”