Question

A particle having a mass of $10^{-2}kg$ carries a charge of $5\times 10^{-8}C$. The particle is given an initial horizontal velocity of $10^{5}m{s}^{-1}$ 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 directionof 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?

• A. (1) and (3)
• B. (3) and (4)
• C. (2) and (3)
• D. (2) and (4)

Answer 1

Answer: (C)

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.