The amount of positive and negative charges in a cup of water ($250$ g) are respectively:

If $10^9$ electrons move out of a body to another body every second, how much time approximately is required to get a total charge of $1$ C on the other body?
1. $200$ years
2. $100$ years
3. $150$ years
4. $250$ years

If a body is charged by rubbing it, its weight:

Given below are four statements: 

Choose the correct option:

The ratio of the magnitude of electric force to the magnitude of gravitational force for an electron and a proton will be:
($m_p=1.67\times10^{-27}~\text{kg}$, $m_e=9.11\times10^{-31}~\text{kg}$)
1. $2.4\times10^{39}$
2. $2.6\times10^{36}$
3. $1.4\times10^{36}$
4. $1.6\times10^{39}$

Consider three charges $q_1,~q_2,~q_3$ each equal to $q$ at the vertices of an equilateral triangle of side $l.$ What is the force on a charge $Q$ (with the same sign as $q$) placed at the centroid of the triangle, as shown in the figure?

     
1. $\dfrac{3}{4\pi \epsilon _{0}} \dfrac{Qq}{l^2}$
2. $\dfrac{9}{4\pi \epsilon _{0}} \dfrac{Qq}{l^2}$
3. zero
4. $\dfrac{6}{4\pi \epsilon _{0}} \dfrac{Qq}{l^2}$

Consider the charges $q,~q,$ and $-q$ placed at the vertices of an equilateral triangle, as shown in the figure. Then the sum of the forces on the three charges is:

    

1. $\frac{1}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}$
2. zero
3. $\frac{2}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}$
4. $\frac{3}{4\pi \epsilon _{0}}\frac{q^{2}}{l^{2}}$