Question
Why is the primary winding wire of a voltage step-up transformer usually a larger size than that of the secondary winding?
Answer Options
- A) To improve the coupling between the primary and secondary
- B) To accommodate the higher current of the primary
- C) To prevent parasitic oscillations due to resistive losses in the primary
- D) To ensure that the volume of the primary winding is equal to the volume of the secondary winding
Correct Answer: B
Explanation
A voltage step-up transformer increases the output voltage while simultaneously decreasing the output current. This is due to the principle of conservation of power: the power in the primary roughly equals the power in the secondary (P_p = V_p I_p \approx V_s I_s = P_s).
In a step-up transformer (V_s > V_p), the primary winding voltage is lower, which means the primary winding must carry a higher current (I_p > I_s) to maintain the power balance. Therefore, the wire size of the primary must be larger than the secondary to safely accommodate the higher current without overheating.
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