E! When force is required , just use F=qE where E is already known from an earlier part.
E! When the charge is negative the force on it is opposite to the E at that location.
E! The E vectors arrows are drawn somewhere else not at the location it is required.
E! If two charges are fixed and a third charge is brought near them,find the sum of V due to the two charge first and the work done in bringing the third charge is qV, where q is the third charge and V is the sum of the potential of the two other charges at the location of the third charge.
E! For a parallel plate , the velocity of the electron parallel to the plate suggest that the initial vertical velocity is zero. The equations of motion are v=at, s=0.5at2, v2= 2as.
