Q1. [3] deep thorough-understanding
Oersted demonstrated that a current-carrying conductor deflects a nearby compass needle. A student tries to repeat this observation at home by placing a compass near a live wire in the wall but observes no noticeable deflection. Give TWO reasons, based on principles studied in this chapter, why the deflection is not easily observed in this domestic setting. (Hint: Consider how the magnetic field of a straight conductor depends on current and distance.)
Generated by claude-sonnet-4-6 · 2026-06-26 01:13 · grounding rag
Model Answer
Two reasons why no noticeable deflection is observed:
- Large distance from the wire: The magnetic field due to a straight current-carrying conductor decreases as the distance from it increases. The compass is placed far from the wire inside the wall, so the field at that point is very weak.
- Low current through the wire: The magnetic field strength depends directly on the current flowing through the conductor. Household wires carry only a small current during normal use, producing a magnetic field too weak to noticeably deflect the compass needle.
Source: Chapter 12 – Magnetic Effects of Electric Current, Section 12.2
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Explanation
The examiner expects two distinct, principle-based reasons worth ~1.5 marks each. The two key relationships from the chapter are: (i) B decreases with increasing distance from the wire, and (ii) B increases with current. Mentioning both clearly with a brief justification earns full marks. Avoid vague answers like "the wire is inside the wall" without linking it to the field-distance principle.