When ${10^{14}}$ electrons are removed from a neutral metal sphere, the charge on the sphere becomes......$\mu C$

An infinite number of point charges, each carrying $1 \,\mu C$ charge, are placed along the y-axis at $y=1\, m , 2\, m , 4 \,m , 8\, m \ldots \ldots \ldots \ldots \ldots$

The total force on a $1 \,C$ point charge, placed at the origin, is $x \times 10^{3}\, N$. The value of $x$, to the nearest integer, is .........

[Take $\left.\frac{1}{4 \pi \epsilon_{0}}=9 \times 10^{9} \,Nm ^{2} / C ^{2}\right]$

Two electrons are separated by a distance of $1\,\mathop A\limits^o $. What is the coulomb force between them

Four charges are placed at the circumference of the dial of a clock as shown in figure. If the clock has only hour hand, then the resultant force on a positive charge $q_0$ placed at the centre, points in the direction which shows the time as 

In hydrogen like system the ratio of coulombian force and gravitational force between an electron and a proton is in the order of:

Three charges $ - {q_1},\,\, + {q_2}$ and $ - {q_3}$ are placed as shown in the figure. The $x$-component of the force on $ - {q_1}$ is proportional to