Force on a Current-Carrying Conductor (CIE A Level Physics)

• The strength of a magnetic field is known as the magnetic flux density, B
  • This is also known as the magnetic field strength
  • It is measured in units of Tesla (T)

• The force F on a conductor carrying current I at right angles to a magnetic field with flux density B is defined by the equation

• Where:
  • F = force on a current-carrying conductor in a B field (N)
  • B = magnetic flux density of external B field (T)
  • I = current in the conductor (A)
  • L = length of the conductor (m)
  • θ = angle between the conductor and external B field (degrees)

• This equation shows that the greater the current or the magnetic field strength, the greater the force on the conductor

Magnetic force on a current-carrying conductor

Magnitude of the force on a current-carrying conductor depends on the angle of the conductor to the external B field

• The maximum force occurs when sin θ = 1
  • This means θ = 90^o and the conductor is perpendicular to the B field
  • This equation for the magnetic force now becomes:

• The minimum force (0) is when sin θ = 0
  • This means θ = 0^o and the conductor is parallel to the B field

• It is important to note that a current-carrying conductor will experience no force if the current in the conductor is parallel to the field