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STD 12 - 4. Moving charges and magnetism — NEET STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceNEETSTD 12 - 4. Moving charges and magnetism4 Marks
MCQ
A uniform current carrying ring of mass $m$ and radius $R$ is connected by a massless string as shown. A uniform magnetic field $B_0$ exist in the region to keep the ring in horizontal position, then the current in the ring is  ($l =$ length of string)
  • ✓
    $\frac{{mg}}{{\pi R{B_0}}}$
  • B
    $\frac{{mg}}{{R{B_0}}}$
  • C
    $\frac{{mg}}{{3\pi R{B_0}}}$
  • D
    $\frac{{mgl}}{{\pi {R^2}{B_0}}}$
✓

Answer

Correct option: A.
$\frac{{mg}}{{\pi R{B_0}}}$
a
$\tau_{\text {net }}=0 ; \mathrm{mgR}=\mathrm{MB}_{0}(\mathrm{M}=$ magnetic dipole moment);

$\mathrm{mgR}=\mathrm{I}\left(\pi \mathrm{R}^{2}\right) \mathrm{B}_{0} ; \mathrm{I}=\frac{\mathrm{mg}}{\pi \mathrm{RB}_{0}}$

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