Question

Two parallel metallic plates have surface charge densities `sigma_(1)` and `sigma_(2)` as shown in figure.

`{:(,"Column-I",,,"Column-II"),((A),"If " sigma_(1)+sigma_(2)=0,,(p),"Electric field in region III is towards right"),((B),"If" sigma_(1)+sigma_(2) gt 0,,(q),"Electric field in region I is zero"),((C),"If "sigma_(1)+sigma_(2) lt 0,,(r),"Electric field in region I is towards roght"),(,,,(s),"Nothing can be said"):}`

Answer 1

Correct Answer - (A) r, (B) r, (C) p
Electric field due to metallic plates remains same and constant at near by points.
[A] For `sigma_(1)+sigma_(2)=0 rArr sigma_(0)=-sigma_(2)`
`:.` Electric field at a point is equal & opposite in direction.
`sigma_(1)+sigma_(2)=0 rArr sigma_(1)=-sigma_(2)`
[B] `sigma_(1)+sigma_(2) gt 0 rArr sigma_(1) & sigma_(2)`
either both positive ot opposite but positive has a greater magnitude. So the net electric field will be away from the plates in region I & III.
[C] Same explanation according to [B].