資料來源 : Webster's Revised Unabridged Dictionary (1913)

Electro-magnet \E*lec`tro-mag"net\, n.
   A mass, usually of soft iron, but sometimes of some other
   magnetic metal, as nickel or cobalt, rendered temporarily
   magnetic by being placed within a coil of wire through which
   a current of electricity is passing. The metal is generally
   in the form of a bar, either straight, or bent into the shape
   of a horseshoe.