The output voltage of the ideal transformer with polarities and dots shown in the figure is given by [Figure description: An ideal transformer with turns ratio 1:N. The primary is driven by a source V1 sin(wt) (+ terminal at top). The primary dot is at the top of the primary winding; the secondary dot is at the bottom of the secondary winding (dots on opposite ends, i.e. opposite polarity). The secondary feeds a load (box) with output voltage V2 measured with + at the top and - at the bottom.]
- A. (1/N) V1 sin(wt)
- B. (-1/N) V1 sin(wt)
- C. - N V1 sin(wt)
- D. - N V1 cos(wt)
Answer: C. - N V1 sin(wt)
Explanation: With turns ratio 1:N, primary dot at the top (+), and secondary dot at the bottom (-), the secondary terminal voltage V2 measured positive at the top is inverted: V2 = −N·V1 sin(ωt).