Figure here shows three cases, in all cases the circular path has radius r and straight ones are infinitely long. For same current, the magnetic field at the centre P in cases 1, 2 and 3 have the ratio

Explanation

a) `barB_p = (mu_0i)/(4r)odot`
b) `barB_2 = B_P = 1/2 (mu_0i)/(2r) ox = (mu_0i)/(4r) ox`
c) `barB_p = (3)/(4)(mu_0i)/(2r) ox + (mu_0 i)/(4pi r) odot = (mu_0)/(4)(i)/(r) (3/2 - 1/pi) ox`