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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 rectangular loop carrying a current $i$ is placed in a uniform magnetic field $B$. The area enclosed by the loop is $A$. If there are n turns in the loop, the torque acting on the loop is given by
  • ✓
    $ni\,\overrightarrow A \times \overrightarrow B $
  • B
    $ni\,\overrightarrow A \cdot \overrightarrow B $
  • C
    $\frac{1}{n}(i\overrightarrow A \times \overrightarrow B )$
  • D
    $\frac{1}{n}(i\overrightarrow A \cdot \overrightarrow B )$
✓

Answer

Correct option: A.
$ni\,\overrightarrow A \times \overrightarrow B $
a
(a) $\vec{\tau}=\vec{M} \times \vec{B}$

$=n i(\vec{A} \times \vec{B})(\because \vec{M}=n i \vec{A})$

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