Ferromagnetic material core used for transformer must have

The correct answer is Option (3) → high permeability and low hysteresis loss

The core of a transformer is magnetised and demagnetised in every cycle of the alternating current. It must carry the magnetic flux from the primary to the secondary and must waste as little energy as possible in each cycle.

• A high permeability concentrates the flux in the core, so almost all the flux of the primary links the secondary.

• The energy lost in each cycle equals the area of the hysteresis loop, so a narrow loop (low hysteresis loss) keeps the core from heating up.

Option (1) low permeability and low hysteresis loss — Incorrect. A low permeability would let much of the flux leak out of the core, so the coupling between the coils would be poor.

Option (2) low permeability and high hysteresis loss — Incorrect. Both properties are the wrong way round: poor flux coupling and large energy loss in every cycle.

Option (4) high permeability and high hysteresis loss — Incorrect. A high hysteresis loss wastes energy as heat in every cycle; such materials suit permanent magnets, not transformer cores.

Note: The same question was also asked in CUET (UG) 2023 on 15-06-2023 (Slot 2).

NCERT (2026-27):
Transformers – “… (iv) Hysteresis: The magnetisation of the core is repeatedly reversed by the alternating magnetic field. The resulting expenditure of energy in the core appears as heat and is kept to a minimum by using a magnetic material which has a low hysteresis loss.”