A long straight vertical wire carries a current. Which describes the magnetic field around the wire?
AStraight lines running parallel to the wire in the same direction as the current, spreading out as the distance grows.
BCircles lying in planes that contain the wire, running from the top of the wire to the bottom as in a bar magnet.
CStraight lines pointing away from the wire in every direction, in much the same pattern as the field around a small positive charge.
DCircles centred on the wire, lying in planes at right angles to it, with their direction given by the right hand grip rule.
Explanation
The field of a straight current carrying conductor is a set of concentric circles centred on the wire and lying in planes perpendicular to it. Gripping the wire with the right hand, thumb along the current, the fingers give the direction of the field, and the circles are drawn further apart further from the wire because the field weakens.
Derived from ZIMSEC Combined Science 4003/2, June 2019, Q5(a)