In order to minimise hysteresis loss, the magnetic material should have

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Low hysteresis co-efficient

Explanation: Hysteresis loss in magnetic materials is directly proportional to the area of the B-H hysteresis loop. A material with a low hysteresis coefficient (Steinmetz coefficient) ensures a narrow loop, thereby minimizing the energy dissipated as heat during each cycle of magnetization and demagnetization.

Working Principle: According to the Steinmetz hysteresis loss formula, the energy dissipated per unit volume per cycle is given by $W_h = \eta B_{max}^x$. Here, $\eta$ represents the hysteresis coefficient. By selecting materials with a small $\eta$, such as soft iron or silicon steel, we reduce the energy losses incurred by the molecular friction of magnetic domains rotating against the external field.

Key Formulas: $P_h = \eta f B_{max}^x V$; Area of B-H loop $\propto$ Hysteresis Loss

Key Points: Hysteresis loss occurs due to the energy required to orient magnetic domains.; Soft magnetic materials exhibit low coercivity and narrow B-H loops.; Silicon steel is commonly used in transformers to maintain low hysteresis loss.; The exponent '$x$' typically ranges between 1.6 to 2.0 based on the material.

Advantages: Increased efficiency of electrical machines; Reduced heating of the magnetic core

Disadvantages: High purity materials with low $\eta$ are often more expensive; Extreme magnetic softness can limit maximum flux density

Applications: Transformer cores; Inductor cores; Electric motor laminations

Additional Info: Option B is incorrect because a large B-H loop area implies high hysteresis loss (suitable for permanent magnets, not transformers).. Option D (High resistivity) is used to minimize Eddy Current loss, not hysteresis loss.

Answer: C is correct — A low hysteresis coefficient (Steinmetz coefficient) results in a narrow B-H loop, which directly minimizes the energy lost as heat per cycle.

Exam Tip: Always distinguish between hysteresis loss (reduced by material selection) and eddy current loss (reduced by laminating the core and increasing resistivity).

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