Magnetic Field
Electricity and Magnetism

Force in a third direction

Teaching Guidance for 14-16 Supporting Physics Teaching

Keeping the three directions in mind: current; field; force

Hans Christian Ørsted (1777–1851) was a Danish physicist and chemist who is most widely known for observing that electric currents produce a magnetic field. In the case of a straight conducting wire, the magnetic field lines are circular in shape, centred on the line of the wire.

When a current-carrying wire is placed in the space between two attracting magnets a force acts on the current-carrying wire. This is perhaps not surprising since the current-carrying wire is a magnet and it therefore experiences a force when placed in a magnetic field. What is surprising is the direction of the force on the wire.

The force on the current carrying wire:

  • Is not in the direction of the current in the wire.
  • Is not in the direction of the magnetic field between the attracting magnets.
  • Is in a third direction: at right-angles to both the wire and the field.
Magnetic Field
is used in analyses relating to Solenoid Magnet MRI Scanner Particle Accelerator
can be represented by Field Line
can be determined for a Star
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