A bar magnet of length l and magnetic dipole moment M is bent in the form of an arc as shown in figure. The new magnetic dipole moment will be

Step-by-step solution

Given, ( =60^ = 3 rad ) The new magnetic length of the dipole will be, (I^ =r ) Now, (M=m I ) and (M^ =m I^ ) ( M M ^ = I I ^ (1) ) Now, angle in radians (= arc length radius ) ( 3 = 1 r 1= r 3 ) In the equilateral triangle, marked by dotted lines, (I^ =r ) ( 1 I^ = 3 (2) ) From and, we get, ( aligned & M M^ = 3 & M^ = 3 M aligned ) Hence, ((C) ) is the correct answer. Alternative method: Using the short cut formula about bending of a bar magnet, (M= 2 M ( 2 ) ) (= 2 M 30^ 3 = 3 M ) Hence, (C) is the correct answer