The charge on $500~\text{cc}$ of water due to protons will be: 

A polythene piece rubbed with wool is found to have a negative charge of $3 \times10^{-7}~\text{C}.$ Transfer of mass from wool to polythene is:
1. $0.7\times10^{-18}~\text{kg}$
2. $1.7\times10^{-17}~\text{kg}$
3. $0.7\times10^{-17}~\text{kg}$
4. $1.7\times10^{-18}~\text{kg}$

A total charge $Q$ is broken in two parts $Q_1$ and $Q_2$ and they are placed at a distance $R$ from each other. The maximum force of repulsion between them will occur, when:

Two charges $+2$ C and $+6$ C are repelling each other with a force of $12$ N. If each charge is given $-2$ C of charge, then the value of the force will be:

The acceleration of an electron due to the mutual attraction between the electron and a proton when they are $1.6~\mathring{A}$ apart is:
$\left(\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9~ \text{Nm}^2 \text{C}^{-2}\right)$

Four charges are arranged at the corners of a square $ABCD$ as shown in the figure. The force on a positive charge kept at the center of the square is:

Five balls numbered $1$ to $5$ are suspended using separate threads. Pairs $(1, 2), (2, 4),$ and $(4, 1)$ show electrostatic attraction, while pairs $(2, 3)$ and $(4, 5)$ show repulsion. Therefore ball $(1)$ must be:

1. positively charged
2. negatively charged
3. neutral
4. made of metal

Three charges are placed at the vertices of an equilateral triangle of side $a$ as shown in the following figure. The force experienced by the charge placed at the vertex $A$ in a direction normal to $BC$ is: 

1. $Q^{2} / \left(\right. 4 \pi \epsilon_{0} a^{2} \left.\right)$

2. $- Q^{2} / \left(\right. 4 \pi \epsilon_{0} a^{2} \left.\right)$

3. zero

4. $Q^{2} / \left(\right. 2 \pi \epsilon_{0} a^{2} \left.\right)$

Two small spheres each having the charge $+Q$ are suspended by insulating threads of length $L$ from a hook. If this arrangement is taken in space where there is no gravitational effect, then the angle between the two suspensions and the tension in each will be:

1. $180^\circ,$ $\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{(2 L )^{2}}$

2. $90^\circ,$ $\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{(L )^{2}}$

3. $180^\circ,$ $\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{2 L ^{2}}$

4. $180^\circ,$ $\frac{1}{4 \pi \epsilon_{0}} \frac{Q^{2}}{ L ^{2}}$