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A power transmission line feeds input power at 2300 V to a step-down transformer with its primary windings having 5000 turns. What should be the number of turns in the secondary in order to get output power at 230 V?

Asked in GSEB Board July 2023 · Transformers

• (1) 2300
• (2) 600
• (3) 500
• (4) 400

Step-by-step solution

Why the other options are wrong

• (1) 2300 is the primary voltage, not a number of turns. The secondary turns follow from (Nₛ)/(Nₚ)=(Vₛ)/(Vₚ).
• (2) No single slip gives 600. Sanity check: the voltage is stepped down ten times (2300→230), so the turns must be too: (5000)/(10)=500.
• (4) 400 is what a primary of 4000 turns would give (4000×(230)/(2300)), as in the March 2023 board version of this problem. Here the primary has 5000 turns.

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