This uses the concept of electric current developed in Subtopic 2.1: Potential difference and electric current.
Magnetic fields are associated with permanent magnets and moving charges, such as charges in an electric current.
Current-carrying conductors produce magnetic fields; these fields are utilised in solenoids.
Magnetic field lines can be used to represent the magnetic field. The direction of the magnetic field depends on the direction of the moving charge that is producing the magnetic field.
The magnitude of magnetic field strength, B, at any point is represented by the number of lines crossing a unit area perpendicular to the field in the vicinity of the point.
- Sketch and/or interpret the magnetic field lines produced by a bar magnet, and an electric current flowing in a straight conductor, a loop, and a solenoid.
Video: Crash Course Magnetism (up to 3:49)
Video: Magnetic field around a straight conductor, loop, and solenoid (coil)
The magnitude of the magnetic field strength in the vicinity of a current‑carrying conductor is given by 
where r is the radial distance to the conductor.
• Solve problems involving the use of
• Use vector addition in one dimension or in two dimensions (with right-angled or equilateral triangles) to calculate the magnitude and direction of the magnetic field due to two current-carrying conductors)