If supply frequency in a transformer is doubled by keeping V/f ratio constant.

Correct option is A

​$$\bullet \ \text{Iron losses or core losses of the transformer includes both hysteresis and eddy current losses.} \\[4pt]\bullet \ \text{Hysteresis losses: These are due to the reversal of magnetization in the transformer core whenever it is subjected to alternating nature of magnetizing force.} \\W_h = \eta B_m^{1.6} f v \\\text{Where,} \\\eta = \text{Steinmetz constant} \\B_m = \text{maximum flux density} \\f = \text{frequency of magnetization or supply frequency} \\v = \text{volume of the core} \\[6pt]\bullet \ \text{Eddy current losses: These are basically } I^2R \text{ losses present in the core due to the production of eddy current in the core.} \\W_e = \eta B_m^2 f^2 t^2 \\\text{Where,} \\\eta = \text{Steinmetz constant} \\B_m = \text{maximum flux density} \\f = \text{frequency of magnetization or supply frequency} \\t = \text{thickness of the core} \\[6pt]\bullet \ \text{maximum flux density } (B_m) \text{ is directly proportional to the V/f ratio and V/f ratio is constant, so maximum flux density is also constant.} \\[10pt]\text{Application:} \\[4pt]\bullet \ \text{At a constant V/f ratio} \\W_h \propto f, \quad W_e \propto f^2 \\[6pt]\bullet \ \text{As voltage is increasing by keeping V/f ratio constant} \\\bullet \ \text{i.e. frequency also increased.} \\[6pt]\bullet \ \text{Therefore, both hysteresis and eddy current losses will increase, and hence core losses will increase.} \\[6pt]\bullet \ \text{Magnetizing current is directly proportional to the V/f ratio. As V/f ratio is constant, the magnetizing current will remain the same.}$$​​