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If I put low frequency electric field meter near the connected cable in AC 220V socket, he show 1200 V/m even if device is turn OFF(zero current), if disconnect cable from socket, field drop to 8 V/m.

Why electric filed increase near the wire even if current is zero?

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The electric field depends on the potential difference (voltage) between the wires in the cable, not on the current going through the wires. The electric field will be strongest inside the cable, between the 'live' wire and the 'neutral', and between the live wire and the 'Earth' wire, but the field will also be present outside the cable, forming the well-known field pattern of an electric dipole.

If a current does flow through the wires in the cable (because the device at the end of the cable is turned 'on') there will also be a weak alternating magnetic field in and around the cable. The field will be weak because the cable carries equal currents in opposite directions, but not zero, because the currents are separated by a small distance.

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  • $\begingroup$ Does electric field change polarity even current is zero or field is static? of what particles is el. field made of? $\endgroup$
    – 22flower
    Commented Jul 7 at 12:42
  • $\begingroup$ (a) The field will change polarity at the frequency of the alternating voltage from the socket. This is so whether or not there is current in the cable. (b) Particle theories of electric and magnetic fields represent quite a high level of theoretical Physics, a level to which I don't aspire. $\endgroup$
    – Philip Wood
    Commented Jul 7 at 13:13
  • $\begingroup$ @PhilpWood Is is possible to take energy from this "leaking" ele. field somehow and used it and make some usable work? Of course I mean for higher V/m values.. $\endgroup$
    – 22flower
    Commented Jul 7 at 15:06
  • $\begingroup$ I doubt if the work would be usable, but charged particles near the cable will experience alternating forces from the alternating electric field. This would warm the surface of any conducting material near the cable, owing to work done by the oscillating charge carriers against resistive forces, but the temp rise would surely be too small to detect. If the cable is carrying current you could also theoretically extract energy from the cable's magnetic field by placing a suitably orientated electrically loaded coil of wire near the cable, but the emf induced in the coil would be extremely small. $\endgroup$
    – Philip Wood
    Commented Jul 7 at 15:28

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