Draw a labelled diagram to show the pattern of magnetic field lines produced due to a current carrying straight conductor. Mark on it the direction of current in the conductor and the direction of magnetic field lines.
Generated by claude-sonnet-4-6 · 2026-06-15 06:51 · grounding rag
Model Answer
Diagram:
```
↑ (Current flowing upward)
|
← ——|—— →
( ) | ( ) ← Concentric circles (magnetic field lines)
→ ——|—— ←
|
```
A straight conductor carrying current upward produces concentric circular magnetic field lines around it. By the right-hand thumb rule, if the thumb points in the direction of current, the curled fingers show the direction of magnetic field lines (anticlockwise when viewed from top, for upward current).
Source: Chapter 12, Section 12.2.1 & 12.2.2
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Explanation
- Examiners expect a neat diagram showing the conductor as a straight vertical line with concentric circles around it, arrows on circles showing field direction, and an arrow on the conductor showing current direction.
- Label at least: current direction (↑), magnetic field lines (concentric circles with arrows).
- Mention of right-hand thumb rule for direction earns the second mark.
- The key fact: field lines are circles centred on the wire, not straight lines — this is a common MCQ trap too (Exercise Q1, answer d).