JEE Advanced2008PhysicsMagnetic Effects of CurrentActual
A particle of mass m and charge q , moving with velocity v enters Region II normal to the boundary as shown in the figure. Region II has a uniform magnetic field B perpendicular to the plane of the paper. The length of the Region II is l . Choose the correct choice(s)
Options
- AThe particle enters Region III only if its velocity v> q l B m
- BThe particle enters Region III only if its velocity v < q I B m
- CPath length of the particle in Region II is maximum when velocity v= q I B m
- DTime spent in Region II is same for any velocity v as long as the particle returns to Region I
Correct answer
A. The particle enters Region III only if its velocity v> q l B m
Step-by-step solution
V B in region II. Therefore, path of particle is circle in region II. Particle enters in region III if, radius of circular path, r>1 or m v B q >1 or v> B q l m If v= B q l m , r= m v B q =l , particle will turn back and path length will be maximum as shown in figure in region II. If particle returns to region I, time spent in region II will be t= T 2 = m B q , which is independent of v . correct options are (a), (c) and (d).