P20.4) In the figure to the right, a straight infinite wire carries current to the right. The wire has a mass per length of 10 grams per meter and gravity acts downward with g = 9.8 m/s2. There is a wire above it carrying a current I. The wires are separated by 1 cm.
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Assume the upper wire is held fixed and that the magnetic field generated by the upper wire suspends the lower wire against the force of gravity.
25 A
a) What is the direction of the current in the upper wire? b) What is the magnitude of the current in the upper wire?