Ferromagnetic material used in Transformers must have ______________.
Fill in the blank with the correct answer from the options given below.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → High permeability and Low Hysteresis loss
A transformer core is taken through a full cycle of magnetisation 50 times a second. It must carry as much flux as possible from the primary to the secondary, and waste as little energy as possible in each cycle.
A high permeability concentrates the magnetic flux in the core, so almost all the flux of the primary links the secondary. A low hysteresis loss (a narrow hysteresis loop) means little energy is turned into heat in each cycle of magnetisation. Soft iron has both properties.
Option (1) Low permeability and High Hysteresis loss — Incorrect. Low permeability gives poor flux linkage, and high hysteresis loss heats the core.
Option (2) High permeability and Low Hysteresis loss — Correct. Strong flux linkage with little energy lost per cycle.
Option (3) High permeability and High Hysteresis loss — Incorrect. High hysteresis loss wastes energy as heat in every cycle; such materials suit permanent magnets, not cores.
Option (4) Low permeability and Low Hysteresis loss — Incorrect. Low permeability lets much of the flux leak out of the core, so the coils are poorly linked.
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.”