Q1. [2] medium initial-understanding
A student moves a compass needle closer to a straight current-carrying wire (without changing the current). How does the deflection of the compass needle change, and what does this tell us about the magnetic field?
Generated by claude-sonnet-4-6 · 2026-06-26 01:09 · grounding rag
Model Answer
When the compass is moved closer to the current-carrying wire, the deflection of the needle increases. This tells us that the magnetic field produced by the current is stronger at points closer to the wire. Thus, the magnetic field due to a straight current-carrying conductor is stronger near the wire and decreases with distance.
Source: Chapter 12, Section 12.2 — Magnetic Field due to a Current-Carrying Conductor
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Explanation
- Examiners expect two clear points: (1) deflection increases, (2) this means field strength increases closer to the wire.
- The source (Activity 12.1 & 12.4) shows that the compass needle deflects due to the magnetic field of the current. Field lines being closer together = stronger field (from Section 12.1). Bringing the compass nearer = entering a region of denser field lines = greater deflection.
- Avoid vague phrases like "it changes" — state increases explicitly.