Q1. [3] deep thorough-understanding
A horizontal power line carries current from west to east. A current-carrying aluminium rod is held directly below this power line, parallel to it, also carrying current from west to east. Using the right-hand thumb rule to determine the direction of the power line's magnetic field at the rod's location, and then Fleming's left-hand rule to determine the force on the rod, predict whether the rod is attracted towards or repelled away from the power line.
Generated by claude-sonnet-4-6 · 2026-06-26 01:13 · grounding rag
Model Answer
Step 1 – Direction of magnetic field (Right-Hand Thumb Rule):
The power line carries current from west to east. Holding the conductor in the right hand with the thumb pointing east, the fingers below the wire wrap from north to south (i.e., pointing south). So the magnetic field at the rod's location (directly below) is directed towards the south.
Step 2 – Force on the rod (Fleming's Left-Hand Rule):
- Middle finger (current in rod): points east
- Forefinger (magnetic field): points south
- Thumb (force): points upward, towards the power line
Conclusion: The aluminium rod is attracted towards the power line.
Source: Chapter 12, Sections 12.2.2 and 12.3
---
Explanation
- The examiner expects you to apply both rules in sequence — one mark each for the field direction, force direction, and final conclusion.
- Remember: two parallel conductors carrying current in the same direction attract each other (Ampere's result). This question is a direct application of that principle, but you must show the step-by-step reasoning using the two named rules.
- A common error is pointing the field north instead of south — always curl the fingers below the wire, not above.