Eddy current

An eddy current can be made when you have a solenoid (coil of wire), in which there is a soft iron core. When you connect the solenoid to an AC power source, metal objects held above the cross sectional area of the solenoid are repelled due to Lenz's Law.

Eddy Current Media

• Eddy current brake. The North magnetic pole piece (top) in this drawing is shown further away from the disk than the South; this is just to leave room to show the currents. In an actual eddy current brake the pole pieces are positioned as close to the disk as possible.

• Demonstration of Waltenhofen's pendulum, precursor of eddy current brakes. The formation and suppression of eddy currents is here demonstrated by means of this pendulum, a metal plate oscillating between the pole pieces of a strong electromagnet. As soon as a sufficiently strong magnetic field has been switched on, the pendulum is stopped on entering the field.

• Linear motor field.gif

  A cross section through a linear motor placed above a thick aluminium slab. As the linear induction motor's field pattern sweeps to the left, eddy currents are left behind in the metal and this causes the field lines to lean.

• EI-transformer core interleaved.svg

  Lamination of magnetic cores in transformers greatly improves the efficiency by minimising eddy currents

• EI-transformer core interleaved with flux paths.png

  E-I transformer laminations showing flux paths. The effect of the gap where the laminations are butted together can be mitigated by alternating pairs of E laminations with pairs of I laminations, providing a path for the magnetic flux around the gap.