In the above question, the length of the circular coil is halved! This statement is not taken into consideration at all. So shouldn't the answer be A) 1:2 ??

In the above question, the length of the circular coil is halved! This statement is not taken into consideration at all. So shouldn't the answer be A) 1:2 ?? Use the following Information to answer the next questian Keeping other factofs constant. the length of a circular coil is reduced to half and the radius of each turn is doubled. What is the ratio of the final magnetic moment to the previous magnetic moment? 2202% got right' Answer: Solution: Magnetic moment of a coil is given by, N = Number of turns on the coil = Current in the coil A Area of cross-section of the coa = r = Radius of class-section The magnetic moment of the cod in the first case is given as: Now. the radius of each turn has been doubled New of = The magnetic moment of the coa after increasing the radius is g"en as: Taking the ratio of the magnetic moments, M, Ma(r.) Hence. the ratio of the magnetic moments is 4:1. The correct answer D