You are given a transformer that has 800 turns on its primary coil and 64 turns on its secondary coil. A voltage of 220 V is applied to the primary coil. What is the output voltage?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 17.6 V
In an ideal transformer the same flux links both coils, so the emf per turn is the same in each, and the voltages are in the ratio of the numbers of turns.
\( \displaystyle \frac{V_s}{V_p} = \frac{N_s}{N_p} \;\Rightarrow\; V_s = V_p\,\frac{N_s}{N_p} \)
\( \displaystyle V_s = 220 \times \frac{64}{800} = 220 \times 0.08 = 17.6\,\mathrm{V} \)
The secondary has fewer turns, so this is a step-down transformer and the output must be less than 220 V.