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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
An electron is moving along positive $x$-axis.Auniform electric field exists towards negative $y$-axis. What should be the direction of magnetic field of suitable magnitude so that net force of electron is zero
  • A
    positive $z$- axis
  • ✓
    negative $z$-axis
  • C
    positive $y$-axis
  • D
    negative $y$-axis
✓

Answer

Correct option: B.
negative $z$-axis
b
$\overrightarrow{F_{e}}+\overrightarrow{F_{m}}=0$

$q \vec{E}+q(\vec{V} \times \vec{B})=0 \Rightarrow \vec{E}+\vec{V} \times \vec{B}=0$

$E(-\hat{j})+V B(\hat{i} \times \widehat{n})=0 \Rightarrow \hat{i} \times \widehat{n}$

should be in $\hat{j} . S o \widehat{n}=-\hat{k}$

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