QJEEM17Ph5c59: JEE Main 2017 Physics - Class 12 JEEM17Ph5c59 Solution: A magnetic needle of magnetic moment 6.7 × 10 -2 A m 2 and…

Question

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A magnetic needle of magnetic moment 6.7

\times

10^-2 A m² and moment of inertia 7.5

\times

10^-6 kg m² is performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is:

Accepted Answer

Given : Magnetic moment, M = 6.7 × 10^–2 Am²

Magnetic field, B = 0.01 T

Moment of inertia, I = 7.5 × 10^–6 Kgm²

Using, T =

2 π \sqrt{\frac{I}{M B}}

=

2 π \sqrt{\frac{7.5 \times 10^{- 6}}{6.7 \times 10^{- 2} \times 0.01}}

=

\frac{2 π}{10} \times 1.06

s

Time taken for 10 complete oscillations

t = 10T = 2

π

× 1.06

= 6.6568

≃

6.65 s

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