Same chapter3 marksDifficulty: Medium
A coil of 200 turns experiences a change of flux of 0.02 Wb in 0.1 s. Find the induced emf.
Electromagnetic Induction and Alternating Currents
3 marksDifficulty: Medium
Why is a transformer not usable with direct current, and what are eddy currents?
Original Khojo Papers practice question — not from a past board paper.
Answer
A transformer works by mutual induction and needs a changing flux in the core; a steady direct current gives a steady flux, so no emf is induced in the secondary. Eddy currents are the circulating currents induced in the body of the core by the changing flux, and they waste energy as heat; laminating the core greatly reduces them.
No citable source has been recorded for this record. Treat it as practice material, not as fact.
Explanation
Hysteresis loss is reduced instead by using soft iron for the core.
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