Exam-style question
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A transformer is designed to step down voltage from 400 V to 100 V. If the primary coil has 200 turns, how many turns does the secondary coil have?.
- A.50 turns
- B.100 turns
- C.200 turns
- D.400 turns
Model answer
What a good answer should say
- 50 turns
Explanation
Why this works
Using the turns ratio formula: Np / Ns = Vp / Vs, we can rearrange to find Ns: Ns = Np x (Vs / Vp). Substituting the values, Ns = 200 turns x (100 V / 400 V) = 50 turns.
This shows the number of turns in the secondary coil.
Common mistake
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