Turns Ratio and Polarity

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.