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NEET-XII-Physics

04: Moving Charges And Magnetism

 page 3
Qstn# 23-a Prvs-QstnNext-Qstn
  • #23-a
    the wire intersects the axis,
    (b) the wire is turned from N-S to northeast-northwest direction,
    (c) the wire in the N-S direction is lowered from the axis by a distance of 6.0 cm?
    Ans : If the wire intersects the axis, then the length of the wire is the diameter of the cylindrical region.

    Thus, l = 2r = 0.2 m

    Angle between magnetic field and current, θ = 90°

    Magnetic force acting on the wire is given by the relation,

    F = BIl sin θ

    = 1.5 × 7 × 0.2 × sin 90°

    = 2.1 N

    Hence, a force of 2.1 N acts on the wire in a vertically downward direction.
    (b) New length of the wire after turning it to the Northeast-Northwest direction can be given as: :



    Angle between magnetic field and current, θ = 45°

    Force on the wire,

    F = BIl1 sin θ



    Hence, a force of 2.1 N acts vertically downward on the wire. This is independent of angleθbecause l sinθ is fixed.
    (c) The wire is lowered from the axis by distance, d = 6.0 cm

    Suppose wire is passing perpendicularly to the axis of cylindrical magnetic field then lowering 6 cm means displacing the wire 6 cm from its initial position towards to end of cross sectional area.



    Thus the length of wire in magnetic field will be 16 cm as AB= L =2x =16 cm

    Now the force,

    F = iLB sin90° as the wire will be perpendicular to the magnetic field.

    F= 7 × 0.16 × 1.5 =1.68 N

    The direction will be given by right hand curl rule or screw rule i.e. vertically downwards.
  • #23-b
    the wire is turned from N-S to northeast-northwest direction,
    Ans : New length of the wire after turning it to the Northeast-Northwest direction can be given as: :



    Angle between magnetic field and current, θ = 45°

    Force on the wire,

    F = BIl1 sin θ



    Hence, a force of 2.1 N acts vertically downward on the wire. This is independent of angleθbecause l sinθ is fixed.
  • #23-c
    the wire in the N-S direction is lowered from the axis by a distance of 6.0 cm?
    Ans : The wire is lowered from the axis by distance, d = 6.0 cm

    Suppose wire is passing perpendicularly to the axis of cylindrical magnetic field then lowering 6 cm means displacing the wire 6 cm from its initial position towards to end of cross sectional area.



    Thus the length of wire in magnetic field will be 16 cm as AB= L =2x =16 cm

    Now the force,

    F = iLB sin90° as the wire will be perpendicular to the magnetic field.

    F= 7 × 0.16 × 1.5 =1.68 N

    The direction will be given by right hand curl rule or screw rule i.e. vertically downwards.