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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
A wire carrying a current $I$ is placed inside a uniform magnetic field $\vec B=-B_0\hat k$. The shape of the wire is parabolic and has equation $Y = 2x -x^2.$ The force on the wire will be :
  • ✓
    $F = 2B_0i,$ upwards
  • B
    $F = 2B_0i,$ downwards
  • C
    $F = 4B_0i,$ upwards
  • D
    $F = 4B_0i,$ downwards
✓

Answer

Correct option: A.
$F = 2B_0i,$ upwards
a
$y=2 x-x^{2}=0$

$x=0$

$x=2$

$F=B i \ell$

$=B_{0} i \times 2$

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