An infinite number of straight wires each carrying current I are equally placed as shown in the figure. Adjacent wires have current in the opposite direction. The net magnetic field at point P is

Step-by-step solution

B 1 = μ 0 4 π I a sin α + sin β = μ 0 4 π I × 2 sin 3 0 ∘ a cos 3 0 ∘ B → = B → = B 1 k ^ + B 2 k ^ + B 3 k ^ - B 4 k ^ + ..... = μ 0 4 π I × 2 sin 3 0 ∘ a cos 3 0 ∘ k ^ - μ 0 4 π I × 2 sin 3 0 ∘ 2 a cos 3 0 ∘ k ^ + μ 0 4 π I × 2 sin 3 0 ∘ 3 a cos 3 0 ∘ k ^ + ..... = μ 0 4 π 2 I 3 a k ^ - μ 0 4 π 2 I 3 × 2 a k ^ + μ 0 4 π 2 I 3 × 3 a k ^