An electron is moving along the positive x-ax | vedclass

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(D) The electron has a velocity $\vec{v} = v \hat{i}$. For it to move in an anticlockwise circular path in the $xy$-plane,the initial magnetic force $

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Along the negative $z$-axis

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(D) The electron has a velocity $\vec{v} = v \hat{i}$. For it to move in an anticlockwise circular path in the $xy$-plane,the initial magnetic force $\vec{F}_m$ must be directed along the positive $y$-axis (towards the center of the circular path). Using the Lorentz force formula $\vec{F}_m = q(\vec{v} 	imes \vec{B})$,where $q = -e$ (for an electron),we have: $\vec{F}_m = -e(v \hat{i} 	imes \vec{B}) = F_0 \hat{j}$. This implies $(\hat{i} 	imes \vec{B}) = -\frac{F_0}{ev} \hat{j}$. Since $\hat{i} 	imes \hat{k} = \hat{j}$,we have $\hat{i} 	imes (-\hat{k}) = -\hat{j}$. Therefore,the magnetic field $\vec{B}$ must be directed along the negative $z$-axis.

An electron is moving along the positive $x$-axis. To make it move in an anticlockwise circular path in the $x-y$ plane,a magnetic field must be applied:

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