Force on Current-Carrying Conductors
A wire AB is carrying steady current and is kept on the table. Another wire CD carrying current is held directly above as shown in figure. When the wire CD is left free and it remains suspended at its position, its mass per unit length is (g=acceleration due to gravity, = permeability of free space)

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Answer: (a)
- Currents in AB and CD are opposite, so CD is repelled upward.
- Balance per unit length:
- So the answer is (a).