Moderate

A metal rod PQ (carrying current from P to Q) is placed perpendicular to the infinite long wire carrying current iI0. If this arrangement lies in a horizontal plane; then the rod PQ will rotate:

Correct answer: A. Clockwise

  • A. Clockwise
  • B. Anticlockwise
  • C. Along PQ
  • D. Does not rotate

Explanation

If the given arrangement lies in a horizontal plane; then the rod PQ will rotate clockwise due to the torque. By the right-hand grip rule, the direction of the magnetic field due to current i0 at point P is on the screen. The direction of current in rod PQ is given from P to Q. Hence, the force at point P is towards the top of the screen by Fleming's left-hand rule. Since the rod is pivoted, the rod rotates in a clockwise direction.

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