Why is the core of an electric transformer laminated with thin sheets insulated from each other by varnish rather than being made of a single solid block of iron?

Answer and explanation

Correct answer: B. To reduce energy loss due to eddy currents by increasing electrical resistance along circulation paths

  1. Step 1: In a transformer, alternating magnetic flux induces circulating currents known as eddy currents within the conductive iron core.
  2. Step 2: If the core is solid, these large closed loops encounter low resistance, leading to massive power dissipation in the form of unwanted heat.
  3. Step 3: By slicing the core into thin laminations oriented parallel to the magnetic flux lines and separated by insulating varnish, the closed loop path lengths are constrained and the effective electrical resistance to circulating eddy currents is dramatically increased.
  4. Step 4: Consequently, eddy current magnitudes and associated thermal losses are minimized.
Answer
To reduce energy loss due to eddy currents by increasing electrical resistance along circulation paths
Why not the others: 'To eliminate hysteresis loss' is addressed by selecting a magnetically soft material with a narrow B-H hysteresis loop (such as silicon steel or soft iron), not by lamination; 'To prevent copper loss' refers to heating in the external copper coil windings, which is reduced by using thicker copper wire; 'To increase magnetic permeability' is a material property independent of core lamination.

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