ocr: PRINCIPLES OF SCIENCE ELECTROMAGNETISM LECTRICITY. AND MAGNETISM are Eclosely linked. An electric current always produces a magnetic field, and. a changing ELECTRICITY magneticj field always produces an electric current. SUPPLY this electromagnetic effect passes unnoticed Electromagnetic Often, . - because it is very weak. But in the operation of Waves rd uf " many machines, the effect is invaluable. wIF n COIL OF ELECTROMAGNET IRON CORE WIRE- - Electromagnetic Effects Nr u u A - - Related Machines