Force on a Current-Carrying Conductor (Cambridge O Level Physics)

• A current-carrying conductor produces its own magnetic field
  • When interacting with an external magnetic field, it therefore will experience a force

• A current-carrying conductor will only experience a force if the current through it is perpendicular to the direction of the magnetic field lines
  • A simple situation would be a copper rod placed within a uniform magnetic field
  • When current is passed through the copper rod, it experiences a force which makes it move

Force on a Current-Carrying Copper Rod in a Magnetic Field

A copper rod moves within a magnetic field when current is passed through it

• Two ways to reverse the direction of the force (and therefore, the copper rod) are by reversing:
  • The direction of the current
  • The direction of the magnetic field

• The direction of the force (aka the thrust) on a current carrying wire depends on the direction of the current and the direction of the magnetic field
• All three will be perpendicular to each other
  • This means that sometimes the force could appear to be acting either into or out of the page

• The direction of the force (or thrust) can be worked out by using Fleming's left-hand rule:

Fleming's Left-Hand Rule

Fleming's left-hand rule can be used to determine directions of the force (thumb), magnetic field (first finger) and current (second finger)