What are magnetic field lines ? How is the direction of magnetic field at a point determined ? Draw the pattern of magnetic field lines of the magnetic field produced by a current carrying circular loop. Mark on it the direction of (i) current and (ii) magnetic field lines. Name the two factors on which the magnitude of the magnetic field due to a current carrying coil depends.
Generated by claude-sonnet-4-6 · 2026-06-15 06:50 · grounding rag
Model Answer
Magnetic Field Lines: Magnetic field lines are the paths along which a hypothetical free north pole would tend to move. They are closed continuous curves that indicate the direction and strength of the magnetic field (closer lines = stronger field).
Direction of Magnetic Field at a Point: The direction of the magnetic field at a point is given by the direction in which the north pole of a compass needle points when placed at that point.
Pattern of Magnetic Field Lines for a Current-Carrying Circular Loop:
(Diagram: Concentric-arc field lines around the loop wire, becoming straight lines at the centre; current direction marked with arrows on the loop, field lines with arrows inside the loop pointing towards the reader.)
- (i) Current direction — shown by arrows on the circular loop.
- (ii) Magnetic field lines — emerge as concentric arcs around the wire, appearing as straight parallel lines at the centre; direction determined by the right-hand thumb rule.
Two factors on which the magnitude of magnetic field depends:
- The number of turns in the coil (more turns → stronger field).
- The current flowing through the coil (more current → stronger field).
Source: Chapter 12, Sections 12.2.2 and 12.2.3
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Explanation
- Definition point (1 mark): Always mention "hypothetical free north pole" — this is the textbook definition examiners expect.
- Direction determination (1 mark): Compass needle / north pole direction at that point.
- Diagram (1 mark): Draw a circle with current arrows (use ⊙/⊗ or plain arrows). Show field lines as concentric arcs outside and straight lines at the centre, with direction arrows.
- Two factors (2 marks): The passage explicitly states (i) number of turns and (ii) current strength — both must be named for full marks. Don't mention distance here; the question asks about the coil specifically.