Guidelines and Measurement for Electric and Magnetic Fields
Just as coal enabled the industrial revolution, electricity is the unseen fuel of modern life. The use of electricity results in the production of electric and magnetic fi elds (EMF). There are two types of EMF classifi ed according to the frequency range: ELF fi elds and VLF fi elds. ELF fi elds are defi ned as those having frequencies up to 3 kHz while VLF fi elds cover the frequency range 3-30 kHz. Because of the quasistatic nature of the EM fi elds at these frequencies, electric and magnetic fi elds act independently of one another and are measured separately. Electric fi elds created by voltage and measured in volts per meter are present whenever an electric appliance is plugged in. The appliance need not be turned on for electric fi elds to be detected. Magnetic fi elds, induced by alternating current and measured using the derived quantity magnetic fl ux density in Tesla or Gauss, are present when the appliance is turned on. The strength of EMF decreases as we move away from their sources. EMF exposure is commonly found in and around our homes and offi ces .