PRZEGLĄD ELEKTROTECHNICZNY (Electrical Review), ISSN 0033-2097, R. 88 NR 5a/2012 31 Asher YAHALOM, Moshe EINAT Ariel University Center of Samaria, Ariel, Israel The magnetic dipole moment of a cellular phone Abstract. In the following we measure the magnetic field of a cellular phone. It is found that the magnetic field is comparable to that of the earth's magnetic field at 6,3 cm above the phone. However, the field is not uniform as the earth's magnetic field but bears the unique distribution of a magnetic field induced by a magnetic dipole. The dipole moment is calculated. Recent claims regarding the safety of cellular phones suggest that weak static magnetic fields are induced around the phone, and this field and its gradients may pose a health risk to the user. An experiment was conducted to measure the induced static magnetic field around a cellular phone. 65 µT variations and 18 µT/cm gradients were measured in the magnetic field at about 6 cm from the phone. The influence the measured magnetic fields may have on the user is beyond the scope of this research. Streszczenie. W pracy mierzymy pole magnetyczne od telefonu komórkowego Stwierdzono, że pole magnetyczne telefonu przyjmuje wartości porównywalne z wartościami ziemskiego pola magnetycznego dla odległości około 6,3 cm od telefonu. Jednakże, pole nie ma rozkładu jednostajnego podobnie jak ziemskie pole magnetyczne, lecz wykazuje unikalny rozkład. Wyznaczono moment dipolowy. W najnowszych pracach dotyczących bezpieczeństwa użytkowania telefonów komórkowych twierdzi się, że słabe pola magnetyczne są indukowane wokół telefonu i że pola te mogą stanowić zagrożenie dla użytkownika. Przeprowadzono eksperyment w celu zmierzenia indukowanego statycznego pola magnetycznego wokół telefonu komórkowego. Z pomiarów uzyskano wartości zmienności indukcji na poziomie 65 µT oraz gradienty na poziomie 18 µT/cm dla odległości około 6 cm od telefonu. Określenie wpływu, jaki mogłyby mieć pola o tego typu charakterystyce na użytkownika nie jest przedmiotem rozważań w niniejszej pracy. (Dipolowy moment magnetyczny telefonu komórkowego) Keywords: cellular phone, health risk, dipole moment. Słowa kluczowe: telefon komórkowy, narażenie zdrowia, moment dipolowy. Introduction As the cellular phone becomes a dominant tool in everyday life, suspicions regarding biological influences it might have on the users become relevant. Many investigations were carried out using a direct approach [1-4] as well as using statistical approach [5,6], most of them pointing out the influence that the radiated radio frequency may or may not have on the user. A different claim that has been recently heard is about an influence on the user of the static magnetic field induced by the phone [6-9]. According to this claim, spatial gradients of the static magnetic field are induced in close proximity to the phone (within ~25 cm around the phone), and the exposure to these gradients may be harmful. This claim is strong enough to drive researchers to perform experiments, develop unique patented tools [10] and even to suggest and develop practical solutions to this effect. Before solutions are suggested, there is a need to accurately describe the static magnetic field near the cellular phone, and evaluate quantitatively the gradients if found. In this study an experimental measurement accompanied by an analytical model of the induced static magnetic field near a cellular phone are presented. The induced magnetic field profile is described and some spatial induced gradients are indeed found. It should be noted that the possible biological influence such magnetic field gradients may or may not have on the user is beyond the scope of this research. Experimental Device A Gauss/Tesla meter (Series 9950 produced by FW BELL) shown in Fig. 1a (see also Figure 1b), was used for the magnetic field measurements. The operating principle of the device is based on the Hall Effect. The device probe allows measurement of a magnetic field in two perpendicular axes, parallel and perpendicular to the probe axis. According to the device specifications it is sensitive to fields up to 0,1 µT. The accuracy of the device is  0,2 µT. In practice a jitter of  0,2 µT was observed in the device readings. Also, a slow drift in the device reading of up to 2 µT was observed. Fig. 1a: A Gauss/Tesla meter (Series 9950 produced by FW BELL). a) b) Fig. 1b: Experimental setup diagram (a) and photograph (b). (a) Tesla meter 9950 Ruler Straight line mapping device 6.3cm Probe Cell Phone