Electromagnetism — Question 253

ANSWER

(a) Concentric circles with counterclockwise arrowheads, viewed as drawn. (b) It becomes one third as large.

Worked solution

(a) The right-hand grip rule uses the thumb out of the page along conventional current; curled fingers point counterclockwise.

(b) $B=\mu_0I/(2\pi r)$, so $B\propto1/r$.

Equivalent physically justified methods, alternative valid sketches and consistent units accepted.

Accept sensible significant figures and consistent rounding from stated constants.

Part a: Draw concentric circular field lines centred on the wire.

[1 mark]

Part a: Show counterclockwise arrowheads.

[1 mark]

Part b: Give the one-third factor or equivalent inverse-distance statement.

[1 mark]

Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.