An uncharged metal sphere is placed between two charged parallel plates. Which of the following diagrams correctly represents the pattern of the electric field lines?

Two point charges $Q$ and $-Q/4$ are separated by a distance $x$. Then:

$A$ negative point charge is placed at point $A$ as shown in the figure. The charge is:

Three identical charges are placed at the three corners of an equilateral triangle as shown in the figure. Which of the following statements is true for the electric field $E$ and electric potential $V$ at the center $O$?

$A$ charge $Q$ of mass $m$ revolves around a charge $q$ due to the electrostatic attraction between them. The time period of its motion can be given by the formula:

$A$ total charge $q$ is divided into $q_1$ and $q_2$,which are placed at two vertices of an equilateral triangle of side $a$. The magnitude of the electric field $E$ at the third vertex of the triangle is to be depicted schematically as a function of $x = q_1 / q$. Choose the correct figure.