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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
Two thin long parallel wires separated by a distance $b$ are carrying a current $i$ $amp$ each. The magnitude of the force per unit length exerted by one wire on the other is
  • A
    $\frac{{{\mu _0}{i^2}}}{{{b^2}}}$
  • ✓
    $\frac{{{\mu _0}{i^2}}}{{2\pi b}}$
  • C
    $\frac{{{\mu _0}i}}{{2\pi b}}$
  • D
    $\frac{{{\mu _0}i}}{{2\pi {b^2}}}$
✓

Answer

Correct option: B.
$\frac{{{\mu _0}{i^2}}}{{2\pi b}}$
b
(b) Force per unit length $ = \frac{{{\mu _0}}}{{4\pi }}.\frac{{2{i_1}{i_2}}}{r} = \frac{{{\mu _0}}}{{2\pi }}.\frac{{{i^2}}}{b}$

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