sentences:  Faraday concluded that since no physical link existed between the two windings, the current in the secondary coil must be caused by a voltage that was induced from the first coil, and that the current produced was directly proportional to the rate of change of the magnetic flux.Initially the principles were put to use in the design of transformers, motors and generators where undesirable heating effects were controlled by the use of a laminated core.Early in the 20th century engineers started to look for ways to harness the heat-generating properties of induction for the purpose of melting steel.