Two equal negative charges $-q$ are fixed at the points $(0, a)$ and $(0, -a)$ on the $Y$-axis. $A$ positive charge $Q$ is released from rest at the point $(2a, 0)$ on the $X$-axis. The charge $Q$ will:

Three parallel metal plates,each of area $A$,are placed as shown in the figure. Charges $Q_1$,$Q_2$,and $Q_3$ are given to them. Edge effects are negligible. Calculate the charge on the two outermost surfaces '$a$' and '$f$'.

The adjacent diagram shows a charge $+Q$ held on an insulating support $S$ and enclosed by a hollow spherical conductor. $O$ represents the centre of the spherical conductor,and $P$ is a point such that $OP = x$ and $SP = r$. The electric field at point $P$ will be

Two identical balls having like charges $Q_1$ and $Q_2$ are placed at a certain distance $r$ apart and repel each other with a force $F_1$. They are brought into contact and then moved apart to a distance equal to half their initial separation $(r/2)$. The force of repulsion between them increases $4.5$ times in comparison with the initial value. The ratio of the initial charges of the balls is

$A$ table tennis ball,which has been covered with conducting paint,is suspended by a silk thread so that it hangs between two plates. One plate is earthed,and the other is connected to a high-voltage generator. This ball:

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 $O$?