The unit of permittivity (${\mathrm{\epsilon }}_0$) of space is

• newton-metre² / coulomb²

• coulomb / newton-metre

• coulomb / newton-metre²

• coulomb² / newton-metre²

Two charges each of equal magnitude 3.2 x 10^-19 coulomb but of opposite sign form an electric dipole. The distance between the two charges is 2.4 $\stackrel{\circ }{\mathrm{A}}$. If the dipole is placed in an electric field of 5 x 10⁵ volt/metre, then in equilibrium its potential energy will be

• 3 × 15^-23 joule

• -3.84 × 10^-23 joule

• -6 × 10^-23 joule 

• -2 × 10^-26 joule 

1 newton/coulomb is equivalent to

• 1 C/V

• 1 J

• 1 V/M

• 1 J/C

An electron is moving with velocity v on a circular path of radius r in a transverse electric field B. The specific charge (e/m) of the electron is

• Bvr

• $\frac{\mathrm{\nu }}{\mathrm{Br}}$

• Bvr²

• $\frac{\mathrm{B}}{\mathrm{r\nu }}$

Number of extra electrons in a body of charge -80$\mathrm{\mu }$C, is

• 80 × 10¹⁵

• 80 × 10⁻¹⁵

• 5 × 10¹⁴

• 1.28 × 10⁻¹⁷

If the electric fluxes entering and leaving an enclosed surface respectively are  Φ₁ and Φ_2, the electric charge inside the surface will be

• (Φ₂ − Φ₁) ε₀

• (Φ₁ + Φ₂) / ε₀

• (Φ₂ − Φ₁) / ε₀

• (Φ₁ + Φ₂) / ε₀

177.

Shown below is a distribution of charges. The flux of electric field due to these charges through the surface is

• $\frac{3\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• zero

• $\frac{2\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{{\mathrm{\epsilon }}_0}$

Two point charges + q and + 4q are located at x = O and x = L respectively. The location of a point on the x-axis at which the net electric field due to these two points charges is zero, is

• L / 3

• 2 L

• 4 L

• 8 L

If electric flux entering and leaving an enclosed surface is ${\mathrm{\varphi }}_1$ and ${\mathrm{\varphi }}_2$ respectively, the electric charge inside the enclosed surface will be

• $\left({\mathrm{\varphi }}_1 + {\mathrm{\varphi }}_2\right) {\mathrm{\epsilon }}_0$

• $\left({\mathrm{\varphi }}_2 - {\mathrm{\varphi }}_1\right) {\mathrm{\epsilon }}_0$

• $\left({\mathrm{\varphi }}_1 + {\mathrm{\varphi }}_2\right) / {\mathrm{\epsilon }}_0$

• $\left({\mathrm{\varphi }}_2 - {\mathrm{\varphi }}_1\right) / {\mathrm{\epsilon }}_0$

The electric field in a region is given by E = $\left(4 \stackrel{\wedge }{\mathrm{i}} + 3 \stackrel{\wedge }{\mathrm{j}}\right)$V/m. The net flux passing through a square area of side 4 m parallel to y-z plane is

• 32 V-m

• 16 V-m

• 12 V-m

• 64 V-m