A straight 2.00m, 150gram wire carries a current in a region wherethe earth\'s m

Question

A straight 2.00m, 150gram wire carries a current in a region wherethe earth's magnetic field is horizontal with a magnitude of0.55gauss.

A. What is the minimum amperage that the current in this wire wouldhave to have so that its weight is completely supported by themagnetic force due to earth's field, assuming that no other forcesexcept gravity act on it? Does it seem likely that such a wirecould support this size of current?

B. Show how the wire would have to be oriented relative to theearth's field to be supported this way.

thanks in advance!!

Explanation / Answer

The force on a current carrying wire in a magnetic field is F= I L B Then m g = I L B    and I = m g / (L B) =.15 * 9.8 / (2 * .55) = 1.34 A Since force on individual charges is F=      q (v xB) the direction of the moving charges (the current)must be moving in an E-W direction since B will be directed in the Ndirection as the north pole is a south magnetic pole. Also, the conventional current will be directed Eastward sincethe conventional current is in the direction that positive charges would move-the electrons in the wirewill be moving westward and have negative charge q

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