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4.Moving Charges and Magnetism
medium
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
B
negative $z$-axis
C
positive $y$-axis
D
negative $y$-axis
Solution
$\overrightarrow{F_{e}}+\overrightarrow{F_{m}}=0$
$q \vec{E}+q(\vec{V} \times \vec{B})=0 \Rightarrow \vec{E}+\vec{V} \times \vec{B}=0$
$E(-\hat{j})+V B(\hat{i} \times \widehat{n})=0 \Rightarrow \hat{i} \times \widehat{n}$
should be in $\hat{j} . S o \widehat{n}=-\hat{k}$
Standard 12
Physics
