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Physics · 2026 · 3 marks
CBSE 2026 · Region 5 · Set 3 · Q23
(a) Can a transformer step up or step down dc power supply? (b) Can a step up transformer work as a step down transformer? (c) Does a step up…
(a)
Can a transformer step up or step down dc power supply ?
(b)
Can a step up transformer work as a step down transformer ?
(c)
Does a step up transformer contradict the principle of conservation of energy ? Justify your answer.
Marking-scheme solution
Answering
(a)
No Transformers work on the principle of mutual induction. Because D.C. provides a constant current, there will be no change in magnetic flux. (b) Yes By reversing the connections, the secondary winding can be used as the primary. (c) No A step-up transformer changes low voltage into high voltage, and the current is reduced by the same proportion.
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CBSE Class 12 Physics past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.