Q1. [1] deep thorough-understanding
An overhead power line runs from east to west and carries current in the east-to-west direction. A compass is placed at a point directly below the wire. In which direction does the north pole of the compass needle point?
- A North
- B South
- C East
- D West
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
Answer: B – South
Using the right-hand thumb rule, with current flowing east to west, the magnetic field directly below the wire points towards the south. So the north pole of the compass needle deflects towards south.
Source: Chapter 12, Section 12.2.2 – Right-Hand Thumb Rule (Example 12.1)
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Explanation
- Point your right-hand thumb eastward → westward (direction of current). Your fingers curl downward and southward on the underside of the wire, meaning the field at a point directly below points south.
- Example 12.1 in the textbook confirms: the field turns clockwise when viewed from the east end, so below the wire the field points south.
- The north pole of a compass aligns with the field direction, hence it points south.
- Common mistake: confusing "above" and "below" — above the wire the field points north, below it points south.