Science (086) — AI-generated practice question

(i) A coil of 50 turns produces a much stronger magnetic field than a single loop because the current in each turn flows in the same direction, so the magnetic field due to each turn adds up. The total field at the centre is n times (here 50 times) that produced by a single turn.

(ii) At the centre of a current-carrying circular loop, the magnetic field lines appear as straight parallel lines. This is because the concentric circular field lines around each part of the wire become larger and larger away from the wire. By the time they reach the centre, their arcs are so large that they appear straight. Also, every section of the wire contributes field lines in the same direction at the centre (by the right-hand rule), reinforcing this appearance.

Source: Chapter 12, Section 12.2.3 — Magnetic Field due to a Current through a Circular Loop

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• For part (i), the key phrase examiners look for is "field due to each turn adds up" and "n times as large." Mention same direction of current in all turns.
• For part (ii), the two ideas needed are: (a) arcs of large concentric circles appear straight at the centre, and (b) all sections contribute in the same direction. Both points together earn full credit.
• Avoid vague language like "stronger" without reason — always explain why in terms of the textbook mechanism.