The electric field at a point varies as $r^0$ for-

(1) An electric dipole

(2) A point charge

(3) A plane infinite sheet of charge

(4) A line charge of infinite length

Two point charges A and B having charges +Q and -Q respectively are placed at certain distance apart and force acting between them is F. If 25% charge of A is tranferred to B, then force between the charges becomes:

1. $\frac{4F}{3}$

2. F

3. $\frac{9F}{16}$

4. $\frac{16F}{9}$

Two parallel infinite line charges with linear charge densities $+\lambda C/m and +\lambda C/m$ are placed at a distance R. Electric field mid-way between the two line charges is-

1. $\frac{\lambda }{2{\mathrm{\pi \epsilon }}_0\mathrm{R}}N/C$

2. zero

3. $\frac{2\lambda }{{\mathrm{\pi \epsilon }}_0\mathrm{R}}N/C$

4. $\frac{\lambda }{{\mathrm{\pi \epsilon }}_0\mathrm{R}}N/C$

A sphere encloses an electric dipole with charges $\pm 3\times {10}^{-6}C$. What is the total electric flux through the sphere?

(1) -3$\times {10}^{-6}$

(2) zero

(3) 3$\times {10}^{-6} N{m}^2/C$

(4) 6$\times {10}^{-6} N{m}^2/C$

An electric dipole is placed at an angle of 30 ° with an electric field intensity 2 x 10⁵ N/C. It experiences a torque equal to 4 Nm. The charge on the dipole, if the dipole length is 2 cm, is

1.  8mC

2.  2mC

3.  5mC

4.  

A square surface of side L m is in the plane of the paper. A uniform electric field  (V/m), also in the plane of the paper, is limited only to the lower half of the square surface, (see figure). The electric flux in SI units associated with the surface is : 

1. $E{L}^2/\left(2{\epsilon }_0\right)$

2. $E{L}^2/2$

3. zero

4. $E{L}^2$

A hollow cylinder has a charge q coulomb within it(at the geometrical centre). If ϕ is the electric flux in unit of voltmeter associated with the curved surface B, the flux linked with the plane surface A in unit of voltmeter will be: 

1. $\frac{1}{2}\left(\frac{q}{{\epsilon }_0}-\Phi \right)$

2. $\frac{q}{2{\epsilon }_0}$

3. $\frac{\Phi }{3}$

4. $\frac{q}{{\epsilon }_0}-\Phi$