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5 June, 13:12

A circular wire loop of radius 8.4 m lies in a plane perpendicular to a uniform magnetic field of magnitude 0.4 T. In 0.1 s the wire is reshaped into a square but remains in the same plane. What is the magnitude of the average induced emf in the wire during this time? Answer in units of V.

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  1. 5 June, 13:16
    0
    Given that,

    Circular loop

    Radius of loop

    R = 8.4m

    Area of a circle

    A1 = πr² = π * 8.4² = 221.67m²

    Magnetic field B = 0.4T

    Time take t = 0.1sec

    The wire is reshaped to square

    Length of wire can be calculated using perimeter of a circle

    P = 2πr

    P = 2π * 8.4 = 52.78m

    Which is the length of the square, therefore each side of the square is

    L = 52.78/4 = 13.19m

    Area of a square

    A2 = L² = 13.19² = 174.1

    EMF cam be calculated using.

    EMF = - dΦ/dt

    Where Φ = B•A•Sinθ

    Since the field is perpendicular to the plane. then, θ=90° and Sinθ = 1

    EMF = - dΦ/dt

    EMF = - d (BA) / dt

    B is constant

    EMF = - B•dA/dt

    EMF = - B ∆A/∆t

    EMF = - B * (A2-A1) / (t2-t1)

    EMF = - 0.4 * (174.01 - 221.67) / 0.1

    EMF = - 0.4 * - 47.57 / 0.1

    EMF = 190.28 Volts

    The magnitude of induced EMF is 190.28 V
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