JEE Advanced 2021 Paper 1 Q17 Physics Magnetism Charged Particle Motion in Magnetic Field Medium

JEE Advanced 2021 Paper 1 · Q17 · Charged Particle Motion in Magnetic Field

An α-particle (mass 4 amu) and a singly charged sulfur ion (mass 32 amu) are initially at rest. They are accelerated through a potential V and then allowed to pass into a region of uniform magnetic field which is normal to the velocities of the particles. Within this region, the α-particle and the sulfur ion move in circular orbits of radii r_α and r_S, respectively. The ratio (r_S/r_α) is ___.

Reveal answer + step-by-step solution

Correct answer:4

Solution

From qV = ½mv² ⇒ v = √(2qV/m). Radius r = mv/(qB) = √(2mV/q)/B. So r ∝ √(m/q). r_S/r_α = √[(m_S/q_S)/(m_α/q_α)] = √[(32/1)/(4/2)] = √16 = 4.

Want to drill deeper? Open this question inside SolveKar AI and tap "Why?" on any step — the AI Mentor reads your full solution context and explains until it clicks. Download SolveKar AI →