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Science — CBSE Class 10 board question

Q1. [1]
Assertion (A) : The deflection of a compass needle placed near a current carrying wire decreases when the magnitude of an electric current in the wire is increased. Reason (R) : Strength of the magnetic field at a point due to a current carrying conductor increases on increasing the current in the conductor.
  1. (A) Both (A) and (R) are true and (R) is the correct explanation of (A).
  2. (B) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
  3. (C) (A) is true, but (R) is false.
  4. (D) (A) is false, but (R) is true.
Previously asked in CBSE board exam
2024 31/2/1 Q20
Generated by claude-sonnet-4-6 · 2026-06-15 06:50 · grounding rag
Model Answer

(D) (A) is false, but (R) is true.

The Assertion is false — increasing current increases the deflection of the compass needle, not decreases it. The Reason is true — magnetic field strength increases with increasing current.

Explanation

Examiners expect you to identify that the Assertion directly contradicts what Oersted's experiment shows: greater current → stronger magnetic field → greater deflection of the needle. The Reason is a correct statement of the principle. Option (D) is the only choice where R is true and A is false.

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Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.