Hydrogen ion and singly ionized helium atom are accelerated, from rest, through the same potential difference. The ratio of final speeds of hydrogen and helium ions is close to......

A block of mass $m$ containing a net negative charge $-q$ is placed on a frictionless  horizontal table and is connected to a wall through an unstretched spring of spring  constant $k$ as shown. If horizontal electric field $E$ parallel to the spring is switched on,  then the maximum compression of the spring is :-

The escape speed of an electron launched from the surface of a glass sphere of diameter $1\ cm$ that has been charged to $10\ nC$ is $x \times 10^7\ m/sec$ . The value of $x$ is 

The work done in carrying a charge of $5\,\mu \,C$ from a point $A$ to a point $B$ in an electric field is $10\,mJ$. The potential difference $({V_B} - {V_A})$ is then

Three charges are placed along $x$-axis at $x=-a, x=0$ and $x=a$ as shown in the figure. The potential energy of the system is

Charges $+q$ and $-q$ are placed at points $A$ and $B$ respectively which are a distance $2\,L$ apart, $C$ is  the midpoint between $A$ and $B.$ The work done in moving a charge $+Q$ along the semicircle $CRD$ is