MCQ
In two separate experiments the neutral points due to two small magnets are at a distance of $r$ and $ 2r$ n broad side-on position. The ratio of their magnetic moments will be
- A$4:1$
- B$1:2$
- C$2:1$
- ✓$1:8$
✓
Answer
Correct option: D.
$1:8$
d
(d)At broad side-on position $B = \frac{M}{{{d^3}}}$
$\therefore \,\frac{{{M_1}}}{{d_1^3}} = \frac{{{M_2}}}{{d_2^3}}or\frac{{{M_1}}}{{{r^3}}} = \frac{{{M_2}}}{{8{r^3}}}or\frac{{{M_1}}}{{{M_2}}} = \frac{{{r^3}}}{{8{r^3}}} = \frac{1}{8}$
(d)At broad side-on position $B = \frac{M}{{{d^3}}}$
$\therefore \,\frac{{{M_1}}}{{d_1^3}} = \frac{{{M_2}}}{{d_2^3}}or\frac{{{M_1}}}{{{r^3}}} = \frac{{{M_2}}}{{8{r^3}}}or\frac{{{M_1}}}{{{M_2}}} = \frac{{{r^3}}}{{8{r^3}}} = \frac{1}{8}$
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