InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
A large solid sphere with uniformly distributed positive charge has a smooth narrow tunnel through its centre. A small particle with negative charge, initially at rest far from the sphere, approaches it along the line of the tunnel, reaches its surface with a speed v, and passes through the tunnel. Its speed at the centre of the sphere will be(a) 0 (b) v(c) √2v (d) √1.5v |
|
Answer» Correct Answer is: (d) √1.5v Potential at ∞ = V∞ = 0. Potential at the surface of the sphere = Vs = k Q/R. Potential at the centre of the sphere = Vc = 3/2 k Q/R . Let m and -q be the mass and the charge of the particle respectively. Let v0 = speed of the particle at the centre of the sphere. 1/2 mv2 = - q [V∞ - Vs] = qk Q/R 1/2 mv02 = - q [V∞ - Vc] = q. 3/2 k Q/R. Dividing, v02/v2 = 3/2 = 1.5 or v0 = √(1.5v). |
|