Force Acting on Moving Charges: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Force Acting on Moving Charges. Understanding the underlying formula is key to arriving at the correct answer below:

The magnetic force \( \vec{F}_m = q(\vec{v} \times \vec{B}) \) is always perpendicular to the velocity \( \vec{v} \). Work done by a force is \( W = \vec{F} \cdot \vec{d} \). Since \( \vec{F}_m \perp \vec{v} \), the work done by magnetic force is zero. Thus, both A and R are true, and R correctly explains A.