MODEL RELEASED. Electromagnetic radiation research. Scientist calibrating his electromagnetic radiation meter in a Helmholtz coil. The coil is a device used for producing a region of nearly uniform magnetic field. The purity of the field means that the accuracy of the meter can be checked against it. Once adjusted, the meter will be used to measure the strength of the electromagnetic field generated by electrical devices. An electromagnetic field is produced by the motion of electrically charged particles. There have been some concerns that electromagnetic radiation from domestic electrical devices causes negative health effects, although this theory has not been proven.