4. A infinitely long straight current carrying wire carries current of \( 2 A \) in it. Just above the wire, there is a thin rod hinged to the wire. The rod is perpendicular to the wire. The rod has mass of \( \frac{1}{4} kg \), length of \( 40 cm \) and carries a current of \( 1 A \). Neglect gravity. The hinge is at the center of the rod. Find the initial angular acceleration of the rod.
(A) \( 1.2 \times 10^{-5} rad / s ^{2} \)
(B) \( 3.6 \times 10^{-5} rad / s ^{2} \)
(C) \( 2.4 \times 10^{-5} rad / s ^{2} \)
(D) \( 4.8 \times 10^{-5} rad / s ^{2} \)