A charged particle goes undeflected in a region containing electric and magnetic field. It is possible that
(i) `vec(E) || vec(B). vec(v) || vec(E)`
(ii) `vec(E)` is not parallel to `vec(B)`
(iii) `vec(v) || vec(B)` but `vec(E)` is not parallel to `vec(B)`
(iv) `vec(E)||vec(B)` but `vec(v)` is not parallel to `vec(E)`

Options

A. `vec(E)||vec(B),vec(v)||vec(E)`
B. `vec(E)` is not parallel to `vec(B)`
C. `vec(v)||vec(B)` but `vec(E)` is not parallel to `vec(E)`
D. `vec(E)||vec(B)` but `vec(v)` is not parallel to `vec(E)`.

Answer

A,B,C,D

Explanation

If `B & E & v` are in same direction then particle will be undeflected cause `vec(F_(M))=0`
`(b)` is also possible is not parallel to `vec(B)`
If `vec(F_(M))=qvB` and `vec(F_(E))=qE` then v is `_|_` to `vec(E)` and v is `_|_` to `vec(B) vec(E)` is not parallel to `vec(B)`