question_answer

Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moment\[\vec{m}.\]Which configuration has highest net magnetic dipole moment?                     

a.	b.
c.	d.

 

A)  1              

B)  2

C)  3            

D)  4

Correct Answer: C

Solution :

a. b. \[\underset{m}{\overset{m}{\longleftrightarrow}}\Rightarrow {{M}_{2}}=0\] c. \[{{M}_{3}}=m\sqrt{{{\left( 1+\cos {{30}^{o}} \right)}^{2}}}\] \[=m\sqrt{\left( 1+\frac{\sqrt{3}}{2} \right)2=m\sqrt{2+\sqrt{3}}}\] d. \[{{M}_{4}}=2m\cos {{30}^{o}}=m\sqrt{3}\]