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NDA 2019 GAT · General Knowledge · Magnetism and Electromagnetic Induction · medium

An ideal transformer steps down 220 V to 11 V. If its primary coil has 1000 turns, the number of turns in the secondary coil is

Single correct option

An ideal transformer steps down 220 V to 11 V. If its primary coil has 1000 turns, the number of turns in the secondary coil is
  1. A. 20
  2. B. 200
  3. C. 550
  4. D. 50
Show answer and solution

Answer: (D) 50

For an ideal transformer Vs/Vp = Ns/Np. So Ns = 1000 x 11/220 = 50 turns. A step-down transformer always has fewer turns in the secondary. The value 20 would come from inverting the ratio.
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Original question written in the NDA 2019 GAT pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake