Figure shows the electric lines of forces emerging from a charged body. If the electric field at A and B are E_A and  E_B respectively and if the displacement between A and B is r, then

• E_A > E_B

• E_A < E_B

• E_A = E_B/r

• E_A = E_B / r²

A small piece of metal wire is dragged across the gap between the pole pieces of a magnet in 0.4 sec. If magnetic flux between the pole pieces is known to be 8 × 10^-4 Wb, then induced emf in the wire, is

• 4 × 10^-3 V

• 8 × 10^-3 V 

• 20 × 10^-3 V

• 6 × 10^-3 V

$\frac{\mathrm{Q}}{{\mathrm{\epsilon }}_{\mathrm{o}}}$

• $\frac{\mathrm{Q}}{6{\mathrm{\epsilon }}_{\mathrm{o}}}$

• $\frac{\mathrm{Q}}{6 {\mathrm{\epsilon }}_{\mathrm{o}}}$

• $\frac{\mathrm{Q}}{{\mathrm{\epsilon }}_{\mathrm{o}} {\mathrm{a}}^2}$

• $\frac{\mathrm{Q}}{4{\mathrm{\pi \epsilon }}_{\mathrm{o}}{\mathrm{a}}^2}$

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

• $\frac{\mathrm{B}}{\mathrm{r\nu }}$

Two spheres of same metal have radii a and b. Thet have been connected to a conducting wire. Find the ratio of the electric field intensity upon them.

• a/b

• b/a

• b² / a

• b²/a²

Using mass (M), length (L), time (T ) and current (A) as fundamental quantities, the dimension of permeability is

• [ M^-1 L T^-2 A ]

• [ M L² T^-2 A^-1 ]

• [ M L T^-2A^-2 ]

• [ M L T^-1 A^-1 ]

10.

Length cannot be measure by

• fermi

• micron

• debye

• light year