PhysicsMedium116×since 2002Q7684A coil having N turns is wound tightly in the form of a spiral with inner and outer radii 'a' and 'b' respectively. Find the magnetic field at centre, when a current I passes through coil:Aμ0IN2(b−a)loge(ba){{{\mu _0}IN} \over {2(b - a)}}{\log _e}\left( {{b \over a}} \right)2(b−a)μ0INloge(ab)Bμ0I8[a+ba−b]{{{\mu _0}I} \over 8}\left[ {{{a + b} \over {a - b}}} \right]8μ0I[a−ba+b]Cμ0I4(a−b)[1a−1b]{{{\mu _0}I} \over {4(a - b)}}\left[ {{1 \over a} - {1 \over b}} \right]4(a−b)μ0I[a1−b1]Dμ0I8(a−ba+b){{{\mu _0}I} \over 8}\left( {{{a - b} \over {a + b}}} \right)8μ0I(a+ba−b)Check answerSkip