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A 2 A current carrying straight metal wire of resistance 1 , resistivity 2 10-6 , area of cross-section 10 mm2 and mass 500 g is suspended horizontally in mid air by applying a uniform magnetic field B. The magnitude of B is 10-1 T (given, g = 10 m/s2).
5
L = RA = 1 10 10-62 10-6 = 5 m
Wire floats ⇒ ILB = mg (B perpendicular to the wire)
B = mgIL = 0.5 102 5
= 0.5 T = 5 10-1 T
Answer: 5
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