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JEE Main 20172 April
Exam
JEE Main
Year
2017
Date
2 April
Subject
Physics
Chapter
Magnetic Properties of Matter

JEE Main 2017 · 2 April · Physics · Magnetic Properties of Matter

A magnetic needle of magnetic moment 6 .7 × 10 ^ - 2 A m ^ 2 and...

A magnetic needle of magnetic moment 6.7×10−2Am26 .7 \times {10}^{- 2}A{m}^{2} and moment of inertia 7.5×10−6kgm27 .5 \times {10}^{- 6}kg{m}^{2} is performing simple harmonic oscillations in a magnetic field of 0.01T0 . 01T. Time taken for 1010 complete oscillations is:

Options

  1. A8.76s8 . 76s
  2. B6.65s6 . 65s
  3. C8.89s8 . 89s
  4. D6.98s6 . 98s

Correct answer

B. 6.65s6 . 65s

Step-by-step solution

Time period of oscillating magnetic needle is T=2πIMBT = 2\pi\sqrt{\dfrac{I}{MB}}

=2π7.5×10−66.7×10−2×0.01sec= 2\pi\sqrt{\dfrac{7.5 \times {10}^{- 6}}{6.7 \times {10}^{- 2} \times 0.01}}sec

=0.6647sec= 0.6647sec

Time for oscillations, t=10T=6.647sec=6.65sect = 10T = 6.647sec = 6.65sec
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