The Shielding Effectiveness of a Magnetic Fluid in Radio Frequency Range

This article builds on the previous work and describes the interaction of transformer oil-based magnetic fluid (MF) with the radio frequency (RF) magnetic near-field. Three prepared samples of the MF used as a barrier to magnetic near-field, consist of transformer oil and dispersed magnetite nanoparticles coated with oleic acid. We pay attention to the important area related to the electromagnetic field shielding by the MF. Such sample of the MF may be a good candidate for applications where it is necessary to simultaneously electrically isolate, remove the excess of heat and to shield electromagnetic interference (EMI). We present a method for the determination of shielding effectiveness (SE) of the MF under RF excitation conditions ranging from 500 MHz to 3 GHz. We report the effect of magnetic volume fraction in the MF and the effect of the sample thickness on the SE

Additional Modification of Thermomagnetic Properties of Objects of Low Relative Permeability in Electromagnetic Field

This paper presents the characteristics of the foodstuff heating phenomenon using induction heating process by an induction cooker. The simulation setup was prepared according to the proposed magnetic material and configuration of the pot and induction cooker. The material properties of pot were varied among the several alternatives. The helical coil was designed on the base of the limitation of the induction cooker size and given number of coil turns and coil tube diameter with specific supplied electric current density. The data from the simulation analysis have to determine the enhancing of the highest heat transfer from induction cooker into pot. These data led to the modification of the material and geometrical properties of the pot in accordance to a minimum heating time and enhanced safety operation, especially close to unshielded magnetic objects

Influence of Electromagnetic Shield on the High Frequency Electromagnetic Field Penetration through the Building Material

This paper studies how to protect people against electromagnetic radiation inside a building. Widespread usage of the mobile communication led to building of more and more new GSM base-station antennas. These antennas are often placed in the areas with high population density. These antennas emit electromagnetic radiation in standard mobile operator frequencies, i.e. 0.9, 1.8 and 2.1 GHz. Many studies have shown potential biological and thermal effects of GSM electromagnetic fields, therefore people are concerned about their health. Electromagnetic wave does not penetrate the wall of the building as a whole. A small part of the wave is reflected and a small part is absorbed by the building material. In this paper the penetration of electromagnetic waves through the commercially available building materials is measured with specific focus on frequencies of 0.9, 1.8, and 2.1 GHz. Next, the surface of the chosen building material was coated with a magnetic conductive paint in order to improve the shielding effect of the building material. The results of experiment show how the electromagnetic shield reduces the penetration of electromagnetic waves through the building wall