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    Re: Test your magnetic compass.
    From: Ken Muldrew
    Date: 2012 Nov 16, 16:01 -0700

    On 2012-11-16, at 2:55 PM, Bill Morris wrote:

    Can some physicist or power engineer explain how an alternating current can produce a constant magnetic field? Could corona discharge really account for the observation or must we postulate rusty joints in transmission towers acting as rectifiers?

    AC power lines produce AC magnetic fields, but you have to be within about a meter of the line for the strength of the B field to equal that of the earth. DC power lines are becoming more popular due to advances in power engineering. Currently there are only about one or two hundred DC high voltage lines worldwide but this number will increase soon (at least power companies seem to be marketing the safety of DC lines pretty aggressively, and they do make sense for technologies such as wind power).

    Ken Muldrew.
       
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