1.

Electric field given by the vector vec E = x hat i + y hat j is present in the x y plane. A small ring carrying +Q, which can freely slide on a smooth nonconducting rod, is projected along the rod from the point (0, L) such that it can reach the other end of the rod. What minimum velocity should be given to the ring ? (Assume zero gravity). .

Answer»

`(Q L^2//m)^(1//2)`
`2(Q L^2//m)^(1//2)`
`4(Q L^2//m)^(1//2)`
zero

Solution : `Delta K + Delta U = 0`
or `(0 + (1)/(2) mv^2) + q Delta V = 0`
`underset(V_(2))overset(V_(1))(int) d V = - [ int E_x d x + int E_y d y]`
`Delta V = - [underset(0)overset(L)intx d x + underset(L)overset(0)(int) y dy] = 0`
HENCE `v = 0`.


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