The magnetic field is a field, produced by electric charges in motion. It is a field of force causing a force on material like iron when placed in the vicinity of the field. Magnetic field does not require any medium to propagate; it can propagate even in a vacuum. Also, the energy storing capacity of the magnetic field is greater than the electric field, this distinguishes magnetic field from the electric field, and therefore it is utilised in almost every electromechanical devices like transformers, motors and generators. Earth also has its natural magnetism which protects it from solar waves from the sun. Further, it provides an operating field for a magnetic compass to operate.
Permanent magnets have their own magnetism, and they are made up of ferromagnetic material like iron or nickel or alnico alloys, while electromagnets are coils which produce the magnetic field when an electric current passes through the coil.
For example, a current carrying conductor produces a magnetic field around the conductor, whose direction is determined by Right-Hand Screw Rule and the strength of field can be varied in accordance with the amount of current flowing in the conductor around the coil. Electromagnets are utilized in various industries for various production and manufacturing processes. The magnetic field has both North pole and a South pole. Monopole does not exist for a magnetic field, unlike electric field where a charge can be isolated. The field line forms a closed loop, as it emanates from North and terminates to South outside a magnet and from south pole to north pole inside a magnet.
At any point on the field, it has both magnitude and direction, so it is represented by a vector. Magnetic field finds its application in almost every electromechanical devices like electric motors and generators. When a current carrying coil is placed in a magnetic field, it experiences a torque. This principle of operation is utilised in electric motor where magnetic torque is produced which exerts a rotating torque on the rotor while in case of generators magnetic field provides a medium for energy exchange between stator and rotor via induction principle. In case of a 3 phase motor, a rotating magnetic field is produced by the 3 phase windings displaced 120 degrees in space. A rotating magnetic field rotates with synchronous speed in the air gap of machines which is required for synchronous motor and induction motors to operate. In order to provide a magnetic medium, machine draws magnetizing current which degrades the power factor of the system. Poor power factor increases the burden on the power system components like transformer and generators, but it is an equally essential component for almost every electromechanical device to operate.