Question

A magnetic needle vibrates in a vertical plane parallel to the
magnetic meridian about a horizontal axis passing through
its centre. Its frequency is n. If the plane of oscillation is
turned about a vertical axis by 90°C, the frequency of its
oscillation in vertical plane will be
(a) n (b) zero
(c) less than n (d) more than n

Answer 1

Answer:

$n = 2\pi \sqrt{ \frac{mb}{i} }$

When it is turned by an angle 90°,

the effective field is vertical V and B>V

So, new frequency <n.

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