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SarkariResultOutBMS · 2024

Previous Year Question

The ideal transformer in Fig. Q49 has N2/N1 = 10. What will be the ratio V2/V1? Fig. Q49
Original source figure for BMS Electrical question 49
Original figure referenced in question 49.
  1. 10
  2. 0.1
  3. – 0.1
  4. – 10

Correct answer: D

Explanation

For an ideal transformer, voltage magnitude follows the turns ratio, |V2/V1|=N2/N1=10. The dot/polarity marking in the figure makes the referenced secondary voltage opposite in polarity to the referenced primary voltage, so V2/V1=−10.

Formula

V2/V1=−N2/N1=−10

Step-by-step solution

Turns Ratio and Polarity explanatory diagram

Correct Answer

D — – 10

Concept and Reasoning

For an ideal transformer, voltage magnitude follows the turns ratio, |V2/V1|=N2/N1=10. The dot/polarity marking in the figure makes the referenced secondary voltage opposite in polarity to the referenced primary voltage, so V2/V1=−10.

Calculation / Key Relation

V2/V1=−N2/N1=−10

Exam Takeaway

Turns ratio gives magnitude; dot convention determines the sign.

Common Mistake

Do not ignore the indicated voltage reference directions and dot polarity.

Common mistake

Do not ignore the indicated voltage reference directions and dot polarity.

Exam tip

Turns ratio gives magnitude; dot convention determines the sign.

Quick method

Turns ratio gives magnitude; dot convention determines the sign.