Electric Charges and Fields Quiz-2

Electric field: electric field intensity, electric field (intensity) due to a point charge, electric field lines, electric dipole, electric field due to a dipole, torque on a dipole placed in a uniform electric field.

1. The negative and positive charges of a dipole of dipole moment $\vec{p}$ are placed respectively at points $\hat{i}a$ and $+\hat{i}a$. If $y>>a$, then the electric field intensity due to the dipole at the point located at $\hat{j}y$ is

$\vec{p}/ {4 \pi \epsilon_0 y^3}$

$-\vec{p}/ {2 \pi \epsilon_0 y^3}$

$\vec{p}/ {2 \pi \epsilon_0 y^3}$

$-\vec{p}/ {4 \pi \epsilon_0 y^3}$

2. The ratio of electric field intensity due to an electric dipole at an axial point to that at an equatorial point at the same distance from centre is

$4:1$

$1:2$

$2:1$

$1:1$

3. If the electric field is uniform, then the electric lines of force are

convergent

parallel

circular

divergent

4. The dimension of Electric field intensity $\vec{E}$ is

$[M L T^{-1} I^{-3}]$

$[M L T^{-2} I^{-1}]$

$[M L T^{-3} I^{-1}]$

$[M^{2} L T^{-3} I^{-1}]$

5. The SI unit of electric dipole moment is

Coulomb-Newton

Newton/Coulomb

Joule/Coulomb

Coulomb-meter

6. The electric lines of force due to an isolated positive point charge are

convergent

parallel

elliptical

divergent

7. The electric field due to an electric dipole at a distance $r$ from its centre is directly proportional to

$\frac{1}{r^3}$

$\frac{1}{r}$

$\frac{1}{r^2}$

$\frac{1}{r^4}$

8. Two equal and opposite charges of $2\times 10^{-10} C$ are placed at a distance of $1 cm$, forming a dipole, and are placed in an electric field of $2 \times 10^5 N/C$. The maximum torque on the dipole is

$2\sqrt{2}\times 10^{-2} Nm$

$4 \times 10^{-2} Nm$

$2\sqrt{2}\times 10^{-6} Nm$

$4 \times 10^{-7} Nm$

9. The magnitude of force experienced by an electron placed at a point in the electric field $\vec{E}$ is equal to its weight $m\vec{g}$. The magnitude of $\vec{E}$ is

${mg}/e$

$e^2/{(mg)}$

${mg}/{e^2}$

$mge$

10. Six charges $+q$ each are placed at the corners of a regular hexagon of side $a$. The electric field at the centre of the hexagon is

$\frac{1}{4\pi\epsilon_0} \frac{q}{a^2}$

$0$

$\frac{1}{4\pi\epsilon_0} \frac{3q}{a^2}$

$\frac{1}{4\pi\epsilon_0} \frac{6q}{a^2}$