Q. Applying the theory of the ‘Right Hand Rule’, a longitudinal surface defect in a round bar is detected by ‘current passing in a direction parallel to the direction of expected defects’ because:

• (A) The current direction is in line with the defect
• (B) The magnetic field is at right angles to the defect
• (C) It makes no difference
• (D) The magnetic field is parallel to the defect