A particle having a mass of $10^{-2} \mathrm{~kg}$ carries a charge of $5 \times 10^{-8} \mathrm{C}$. The…
A particle having a mass of $10^{-2} \mathrm{~kg}$ carries a charge of $5 \times 10^{-8} \mathrm{C}$. The particle is given an initial horizontal velocity of $10^5 \mathrm{~ms}^{-1}$ in the presence of electric field $\vec{E}$ and magnetic field $\vec{B}$. To keep the particle moving in a horizontal direction, it is necessary that
(1) $\vec{B}$ should be perpendicular to the direction of velocity and $\vec{E}$ should be along the direction of velocity.
(2) Both $\vec{B}$ and $\vec{E}$ should be along the direction of velocity.
(3) Both $\vec{B}$ and $\vec{E}$ are mutually perpendicular and perpendicular to the direction of velocity.
(4) $\vec{B}$ should be along the direction of velocity and $\vec{E}$ should be perpendicular to the direction of velocity.
Which one of the following pairs of statements is possible?
(1) and (3)
(3) and (4)
(2) and (3)
(2) and (4)
Solution
Both $\vec{B}$ and $\vec{E}$ should be along the direction of velocity and both $\vec{B}$ and $\vec{E}$ are mutually perpendicular and perpendicular to the direction of velocity.
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