QUESTIONS

If the distance between two equal point-charges is halved and their individual charges are doubled, what would happen to the force between them?

The mutual electrostatic force of attraction between two small spheres carrying charges $+0.4 \mathrm{\mu C}$ and $-0.8 \mathrm{\mu C}$ in air is $0.2 \mathrm{N}$. What is the separation between the two spheres?   

In the adjoining figures are shown three particles $\mathrm{A}$, $\mathrm{B}$ and $\mathrm{C}$ which are equally charged. The force acting on $\mathrm{B}$ due to $\mathrm{A}$ is $2.0\times {10}^{-6} \mathrm{N}$. Find out in each Fig.  $\left(\mathrm{ii}\right)$ net force on $\mathrm{B}$.

$\mathrm{ABC}$ is an equilateral triangle of side $10 \mathrm{m}$ and $\mathrm{D}$ is the mid-point of $\mathrm{BC}$. Charges of $+100,-100$ and $+75 \mu \mathrm{C}$ are placed at $\mathrm{B}$, $\mathrm{C}$ and $\mathrm{D}$, respectively. Find the force on a $+1 \mu \mathrm{C}$ charge placed at $\mathrm{A}$.

Two point-charges $q_1=+0.2 \mathrm{C}$ and $q_2=+0.4 \mathrm{C}$ are $0.1$m apart. Find the electric field at a point on the line joining $q_1$ and $q_2$ such that it is $0.05 \mathrm{m}$ away from $q_2$ and $0.15 \mathrm{m}$ away from $q_1$.

Electric charges $\pm 1000 \mathrm{\mu C}$ are placed at points A and B, respectively at a distance of $2 \mathrm{m}$ from each other. Calculate the electric field at a point at equal distance of $4 \mathrm{m}$ from each charge.

Two point-charges of $+1 \mathrm{\mu C}$ and $-1 \mathrm{\mu C}$are kept at a distance of $2 \mathrm{cm}$. They form an electric dipole. This dipole is situated in a uniform electric field of $1\times {10}^5 {\mathrm{NC}}^{-1}$, with dipole moment vector p making an angle of ${30}^{\circ }$ with the field. Calculate, (ii) the torque acting on the dipole. 

Two point-charges of $+1 \mathrm{\mu C}$and $-1 \mathrm{\mu C}$ are kept at a distance of $2 \mathrm{cm}$. They form an electric dipole. This dipole is situated in a uniform electric; field of $1\times {10}^5 {\mathrm{NC}}^{-1}$, with dipole moment vector p making an angle of ${30}^{\circ }$ with the field. Calculate (iii) When would be the torque maximum? How much?