NEET-XII-Physics
36: Permanent Magnets
- #4Let r be the distance of a point on the axis of a bar magnet from its centre. The magnetic field at such a point is proportional to
(a)
1r
(b)
1r2
(c)
1r3
(d) none of thesedigAnsr: dAns : (d) None of these
Magnetic field B due to a bar magnet of magnetic moment M at distance r of the point on the axis of the magnet from its centre is given by
`` B=\frac{{\mu }_{o}}{4\pi }\frac{2Mr}{{\left({r}^{2}-{l}^{2}\right)}^{2}}``
Here, 2l is the length of the magnet.
So, from the above formula, it can be easily seen that `` B\propto \frac{r}{{\left({r}^{2}-{l}^{2}\right)}^{2}}``.
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