Force on Current-Carrying Conductors
Two infinitely long parallel conducting wires and carry currents and , respectively, in the same direction. The wire has uniform mass per unit length and lies on an insulated floor. The wire is kept fixed at a height above the floor. The minimum magnitude of so that the wire does not rise from the floor is: [ is the acceleration due to gravity and is the permeability of free space.]
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Answer: (c)
- Same direction currents attract, so B (above) pulls A upward.
- Upward force per unit length on A:
- A stays on the floor if
- So the answer is (c) .