Transformer secondary current effect: If the number of turns on the secondary of an ideal transformer is increased (with the same primary drive and the same load impedance referred to its own side), what happens to the secondary current?

Introduction / Context:
Transformers trade voltage for current according to their turns ratio. Designers often add turns to the secondary to raise output voltage, but this change also affects current capability and impedance seen by the load. Understanding this inverse relationship helps avoid overloading windings and ensures proper regulation.

Given Data / Assumptions:

• Ideal transformer (negligible losses) for conceptual clarity.
• Primary drive and load impedance (on the secondary side) are unchanged.
• Frequency and core conditions remain the same.

Concept / Approach:

Voltage ratio V_s/V_p = N_s/N_p, while current ratio I_s/I_p = N_p/N_s. Increasing secondary turns N_s raises V_s but reduces I_s for a given power transfer. For the same load impedance, a higher V_s attempts to increase load current, but the transformer's current capability per ampere-turn decreases; overall, at fixed input, the secondary current rating per volt drops as turns increase. In the ideal relation, for a given primary current, I_s decreases when N_s increases because I_s scales inversely with N_s.

Step-by-Step Solution:

Verification / Alternative check:

Power balance (ideal): P_p ≈ P_s → V_p * I_p ≈ V_s * I_s. If V_s rises with more turns and P stays similar (for the same primary drive limits), I_s must decrease proportionally, confirming the inverse relation.

Why Other Options Are Wrong:

• Increase: contradicts the inverse current–turns relation.
• No effect: ignores transformer scaling laws.
• Increase the primary current: not necessarily true as a direct consequence of adding turns; depends on load and regulation, not the immediate current ratio law.
• Reverse polarity: changing turns count does not flip polarity; winding orientation does.

Common Pitfalls:

• Assuming higher voltage automatically means more usable current; copper and core limits constrain current.
• Confusing load current change due to altered voltage with transformer current ratio capability.

Final Answer:

decrease the secondary current