for the first one... consider a closed gaussian surface which completely covers the plate.... when the plate is changed....the net charge remains same..the srea remains same....since every thing in gauss law remains same...so E should also remain same...
Moderation Team
![[Post New]](/templates/default/images/icon_minipost_new.gif){kind=icon}
![[Up]](/templates/default/images/icon_up.gif "[Up]"){kind=icon}
135
