Question

Statement I: If a charged particle is released from rest in a region of uniform electric and magnetic fields parallel to each other, it will move in a straight line.
Statement II: The electric field exerts no force on the particle but the magnetic field does.

• A. Both statement I and II are correct.
• B. Both statement I and II are incorrect.
• C. Statement I is correct but statement II is incorrect.
• D. Statement II is correct but statement I is incorrect.

Answer 1

Answer: (C)

Due to electric field, the force is $\vec{ F }= q \vec{ E }$ in the direction of $\vec{E}$. Since $\vec{E}$ is parallel to $\vec{B}$, the particle velocity $\vec{v}$ (acquired due to force $\vec{ F }$ ) is parallel to $\vec{ B }$. Hence $\vec{ B }$ will not exert any force since $\vec{ v } \times \vec{ B }=0$ and the motion of the particle is not affected by $\vec{B}$.