Power frequency magnetic fields as high as 15,000,000 milligauss are commonly found internally in equipment such as power transformers, motors and generators .Although these fields are almost contained within the equipment ,some leakage will occur. This paper concentrates on magnetic fields in the range of zero to several hundred milligauss. This level of magnetic field may be experienced by the general public as a result of operation of electrical equipment, current carrying lines, house wiring, electrical appliances, lighting equipment or any other device energized by power frequency sources. For those public living close to a line, time spent in these fields may be long or almost all the time, resulting in large exposure. People with higher occupational exposure to magnetic fields were about three times as likely to develop alzheimers as those with low mechanism. This paper also contain interaction mechanism , sources of power frequency magnetic fields such as transmission system and distribution system ,magnetic fields at home, management of magnetic field by several techniques (shielding the under ground cables ,shielding applied to specific region, electromagnetic shielding and active shielding).