State how a magnetic field arises.

On the diagram below, sketch the magnetic field pattern around the long straight current-carrying conductor. The direction of the current is into the plane of the paper.

The long straight conductor is formed into a coil consisting of two separate turns, X and Y. The coil hangs with its axis vertical.

Assume that the turns of the coil each behave as a long straight conductor.

(i) Explain why, when there is a current in the coil, the separation of X and Y decreases.

(ii) The current in the coil is 15 A and the circumference of one turn is 0.48m. In order to restore X and Y to their original separation, a mass of 2.8×10^–4 kg is suspended from turn Y. Estimate the magnetic field strength at X due to Y.

(electric current means) movement of charge;
Do not allow references to current alone – this is in the question.
Do not allow references to charges repelling.

at least two concentric circles;
with clockwise direction indicated;

(i) each turn subject to the magnetic field of the other / field patterns for individual turns combine;
force shown to be attractive by use of direction rule/ by consideration of field pattern / OWTTE; { (can be shown diagrammatically)

(ii) F=(0.280×10^–3×9.81=)2.75×10^–3N;
\(B = \frac{F}{{Il}}\) or correct substitution 2.75×10^–3=B×(15)×0.48;
\(B = \left( {\frac{{2.75 \times {{10}^{ - 3}}}}{{15 \times 0.48}} = } \right)3.8 \times {10^{ - 4}}{\rm{T}}\);