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4. Moving charges and magnetism — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics4. Moving charges and magnetism1 Mark
MCQ
Ionized hydrogen atoms and $\alpha$ -particles with same momenta enters perpendicular to a constant magnetic field $B$. The ratio of their radii of their paths $\mathrm{r}_{\mathrm{H}}: \mathrm{r}_{\alpha}$ will be
  • ✓
    $2:1$
  • B
    $1:2$
  • C
    $4:1$
  • D
    $1:4$
✓

Answer

Correct option: A.
$2:1$
a
$\frac{\mathrm{q}_{\mathrm{H}}}{\mathrm{q}_{\mathrm{\alpha}}}=\frac{1}{2}$

$r=\frac{m v}{q B}$

For same momenta, $r \propto \frac{1}{q}$

$\frac{r_{H}}{r_{\alpha}}=\frac{q_{\alpha}}{q_{H}}=\frac{2}{1}$

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