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A power transmission line feeds input power at 2300 V to a step-down transformer with its primary winding having 4000 turns. What should be the number of turns in the secondary in order to get output power at 230 V?

Asked in GSEB Board March 2023 · Transformers

• (1) 4000
• (2) 40
• (3) 400
• (4) 2300

Step-by-step solution

Why the other options are wrong

• (1) Keeps the secondary equal to the primary. Equal turns give equal voltages, so the output would still be 2300 V: no step-down at all.
• (2) No single slip gives 40. Sanity check: 40 turns would give 2300×(40)/(4000) = 23 V, a tenth of the voltage wanted.
• (4) Copies the primary voltage (2300 V) as if it were a number of turns. The turns must be in the ratio of the voltages, (230)/(2300).

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