天慈 發問時間: 科學其他:科學 · 1 0 年前

有關電學的議題物理問題

A 0.2kg metal rod carrying a current of 10.0A glides on two horizonal rails 0.500m apart. What vertical magnetic field is required to keep the rod moving at a constant speed if the coefficient of kinetic friction between the rod and rails is 0.100?

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  • 1 0 年前
    最佳解答

    Suppose the magnetic field is B (which is a vector and in SI unit), then the force on the rod (due to the magnetic fields) is

    F = I*l x B, I is the current, and l is the length (vector).

    (for more details, check the Biot-Savart Law)

    If the coefficient of kinetic friction between the rod and rail is 0.1, the kinetic friction f would be

    f = (Normal force)*(0.1) = (0.2)(g)(0.1), suppose g = 10, f =0.2.

    Since the rod moves at constant speed, F = f,

    0.2 = f = F = IlB = 10*0.05*B, B = 0.2/(10*0.05) = 0.4 (Tesla)

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