Ferro-magnetic materials used in transformer core must have:

The correct answer is Option (2) → high permeability and low hysteresis loss

The core of a transformer carries an alternating magnetic flux from the primary to the secondary coil, and it is magnetised and demagnetised in every cycle.

• A high permeability sets up a large flux with a small current and keeps it inside the core, linking the secondary.

• The hysteresis loss per cycle equals the area of the hysteresis loop, so a narrow loop (soft iron) wastes little energy as heat.

Option (1) low permeability and high hysteresis loss — Incorrect. Low permeability lets the flux leak out, and a large hysteresis loop heats the core.

Option (2) high permeability and low hysteresis loss — Correct. High permeability gives strong flux linkage, and low hysteresis loss keeps the heating small.

Option (3) high permeability and high hysteresis loss — Incorrect. High permeability is right, but high hysteresis loss wastes energy as heat in every cycle; such hard materials suit permanent magnets, not transformer cores.

Option (4) low permeability and low hysteresis loss — Incorrect. Low hysteresis loss is right, but low permeability gives weak flux and poor linkage between the coils.

Note: The low hysteresis loss in this question is from the latest textbook (2026-27). The high permeability of the core, that soft ferromagnetic cores of electromagnets have high permeability, is printed only in the pre-rationalised textbook (2022-23). It was removed from the latest book, and it also appears to be out of the CUET 2026 syllabus.

Note: The same question was also asked in CUET (UG) 2023 on 20-06-2023 (Slot 3).

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.”

NCERT (Pre-rationalised edition, 2022-23):
Permanent Magnets and Electromagnets – “… Core of electromagnets are made of ferromagnetic materials which have high permeability and low retentivity. … This is the case in transformer cores and telephone diaphragms. The hysteresis curve of such materials must be narrow.”