A long straight wire of length 2 m and mass 250 g is suspended horizontally in a uniform horizontal magnetic field of 0.7 T. The amount of current flowing through the wire will be (g=9.8 m s⁻²):

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(4) 1.75 A. Given: L=2 m, m=0.250 kg, B=0.7 T horizontal, g=9.8 m s⁻². Idea: "suspended" means the magnetic force carries the whole weight, so the wire hangs with no support. Weight: mg=0.250×9.8=2.45 N. Magnetic force on the wire, with the field perpendicular to it: F=BIL. Setting them equal: BIL=mg, so I=(mg)/(BL). I=(2.45)/(0.7×2)=(2.45)/(1.4). I=1.75 A.

A long straight wire of length 2 m and mass 250 g is suspended horizontally in a uniform horizontal magnetic field of 0.7 T. The amount of current flowing through the wire will be (g=9.8 m s⁻²):

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