Question

In two separate experiments the neutral points due to two small magnets are at a distance of r and 2r in broad side-on position. The ratio of their magnetic moments will be

• A. 4 : 1
• B. 1 : 2
• C. 2 : 1
• D. 1 : 8

Answer 1

Answer: (D)

1 : 8

Answer 2

At broad side-on position $B = \frac { M } { d ^ { 3 } }$

$\therefore \frac { M _ { 1 } } { d _ { 1 } ^ { 3 } } = \frac { M _ { 2 } } { d _ { 2 } ^ { 3 } }$ or $\frac { M _ { 1 } } { r ^ { 3 } } = \frac { M _ { 2 } } { 8 r ^ { 3 } }$ or $\frac { M _ { 1 } } { M _ { 2 } } = \frac { r ^ { 3 } } { 8 r ^ { 3 } } = \frac { 1 } { 8 }$