MHTCET 15 May 2024 Shift 2 Paper

Concept:Laminated cores are used to reduce energy losses caused by eddy currents.Explanation:In a transformer, alternating current in the primary coil produces a changing magnetic flux.This changing flux induces eddy currents in the core according to Faraday’s law of electromagnetic induction.Eddy currents flow in closed loops within the core and generate heat, causing power loss.The core is made of thin laminated sheets, each insulated from the next by a thin coating like varnish or oxide.Lamination reduces the thickness $t$ of each conducting layer, which limits the size of eddy current loops.The power loss due to eddy currents is given by:$$P_{\text{eddy}} = \frac{B_{\max}^{2} f^{2} t^{2} V}{6\rho}$$Here, $P_{\text{eddy}}$ is the eddy current loss, $B_{\max}$ is the maximum flux density, $f$ is the frequency, $t$ is the lamination thickness, $V$ is the core volume, and $\rho$ is the resistivity of the core material.Since $P_{\text{eddy}} \propto t^{2}$, reducing $t$ significantly decreases eddy current losses.Thus, laminating the core improves transformer efficiency by reducing eddy current heating.Answer:Option D: reduce eddy current losses in the core.