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Physics · PYQ NEET UG 2026
हिन्दीTwo infinitely long parallel conducting wires A and B carry currents I and 2I, respectively, in the same direction. The wire A has uniform mass per unit length \( \lambda \) and lies on an insulated floor. The wire B is kept fixed at a height h above the floor. The minimum magnitude of h so that the wire A does not rise from the floor is : [g is the acceleration due to gravity and \( \mu_0 \) is the permeability of free space.]
Correct answer · Option 2
\( \frac{\mu_0 I^2}{\pi\lambda g} \)
Explanation
Magnetic force per unit length balancing gravitational force per unit length gives \( \frac{\mu_0 I_1 I_2}{2\pi h} = \lambda g \). Substituting \( I_1 = I \) and \( I_2 = 2I \) gives \( h = \frac{\mu_0 I^2}{\pi\lambda g} \).
