Question

A straight conductor carries a current along the z-axis. Consider the points A(a, 0, 0), B(0, -a, 0), C(-a, 0, 0) and D(0, a, 0) :

• A. All four points have magnetic fields of the same magnitude
• B. All four points have magnetic fields in different directions
• C. The magnetic fields at A and C are in opposite directions
• D. The magnetic fields at A and B are mutually perpendicular

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A All four points have magnetic fields of the same magnitude
B All four points have magnetic fields in different directions
C The magnetic fields at A and C are in opposite directions
D The magnetic fields at A and B are mutually perpendicular

When a straight conductor carries a current along the z-axis the magnetic field produces in XY plane.
Here, all the four points are located on either X or Y axis at distance of magnitude 'a' from origin. Thus all four points have magnetic fields of the same magnitude but in different directions. Also, A and C are located on positive and negative X axis respectively hence, the magnetic fields at A and C are in opposite directions. While A and B are located on positive x axis and negative Y axis hence, the magnetic fields at A and B are mutually perpendicular to each other.