Investigate qualitatively and quantitatively the interaction between a current-carrying conductor and a uniform magnetic field

  • Force is proportional to magnetic field B
  • Force is proportional to current I
  • Force is proportional to length l
  • Maximum force when current carrying wire is at right angles to magnetic field
  • No Force when current carrying wire is parallel to the magnetic field

If  a wire of length l, carrying current I is placed in a magnetic field with field strength B,  then the current carrying conductor experiences a force equivalent to lIBsinθ where θ is the angle between current carrying wire and the direction of magnetic field.


The direction of force is perpendicular to both the current carrying wire and the magnetic field.

We can use the left hand thumb rule to figure out the direction :


Extract from Physics Stage 6 Syllabus © 2017 NSW Education Standards Authority (NESA)