Magnetic Fields of Conductors & Solenoids — A/L Physics

Magnetic Field due to a Long Straight Conductor A current-carrying straight wire produces a circular magnetic field around it. The field lines form concentric circles centered on the wire, with direction given by the right-hand grip rule (thumb along current, fingers curl in field direction). The field strength decreases with distance from the wire. Example: The magnetic field around a high-voltage power line can deflect a compass needle.

Magnetic Field at the Centre of a Circular Coil A single loop of wire carrying current produces a magnetic field perpendicular to the plane of the loop at its centre. For a coil of N turns, the field at the centre is N times that of a single turn, and the direction is given by the right-hand rule (fingers in current direction, thumb points to north pole). Example: This principle is used in moving-coil galvanometers to produce a radial field.