ABSTRACT
This chapter explains the important concepts of electromagnetism and presents simple calculations. The solenoid is very important in electromagnetic theory since the magnetic field inside the solenoid is practically uniform for a particular current, and is also versatile, in as much that a variation of the current can alter the strength of the magnetic field. The laws of magnetic attraction and repulsion can be demonstrated by using two bar magnets. Lifting magnets, incorporating large electromagnets, are used in iron and steel works for lifting scrap metal. Magnetic flux is the amount of magnetic field produced by a magnetic source. Whereas a transmitter or microphone changes sound waves into corresponding electrical signals, a telephone receiver converts the electrical waves back into sound waves. The loudspeaker is used to convert electrical signals into sound waves. A relay is similar to an electric bell except that contacts are opened or closed by its operation instead of a gong being struck.
