Two concentric conducting spherical shells A and B having radii r_A and r_B (r_B > rA) are charged to Q_A and -Q_B $\left(\left|{\mathrm{Q}}_{\mathrm{B}}\right| > \left|{\mathrm{Q}}_{\mathrm{A}}\right|\right)$ . The electric field along a line passing through the centre is

• $\left|{\mathrm{Q}}_{\mathrm{B}}\right| > \left|{\mathrm{Q}}_{\mathrm{A}}\right|$

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Two charged spheres separated by a distance d exert some force (F) on each other. If they are immersed in a liquid of dielectric constant 4, then what is the force exerted, if all other conditions are same ?

• 2F

• 4F

• $\frac{\mathrm{F}}{2}$

• $\frac{\mathrm{F}}{4}$

A charge q is located at the centre of a cube. The electric flux through any face is

• $\frac{4\mathrm{\pi q}}{6 \left(4{\mathrm{\pi \epsilon }}_0\right)}$

• $\frac{\mathrm{\pi q}}{6\left(4{\mathrm{\pi \epsilon }}_0\right)}$

• $\frac{\mathrm{q}}{6\left(4{\mathrm{\pi \epsilon }}_0\right)}$

• $\frac{2\mathrm{\pi q}}{6\left(4{\mathrm{\pi \epsilon }}_0\right)}$

An electron enters uniform electric field maintained by parallel plates and of value E Vm^-1 with a velocity v ms^-1 , the plates are separated by a distance d metre, then acceleration of the electron in the field is

• $\frac{\mathrm{Ee}}{\mathrm{m}}$

• $\frac{-\mathrm{Ee}}{\mathrm{m}}$

• $\frac{\mathrm{Ed}}{\mathrm{m}}$

• $\mathrm{Ee}\frac{\mathrm{d}}{\mathrm{m}}$

The electrostatic field due to a charged conductor just outside the conductor is 

• zero and parallel to the surface at every point inside the conductor

• zero and is normal to the surface at every point inside the conductor

• parallel to the surface at every point and zero inside the conductor

• normal to the surface at every point and zero inside the conductor

A point charge + q is placed at the midpoint of a cube of side a. The electric flux emerging from the cube is

• zero

• $\frac{3 {\mathrm{qa}}^2}{{\mathrm{\epsilon }}_0}$

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

• $\frac{{\mathrm{\epsilon }}_0}{4{\mathrm{qa}}^2}$

Write down the relation between tesla and gauss. 

The number of electron in 2 coulomb of charge is

• 5 × 10²⁹

• 12.5 × 10¹⁸

• 1.6 × 10¹⁹

• 9 × 10¹¹

Which of the following materials is the best conductor of electricity ?

• Platinum

• Gold

• Silicon

• Copper

190.

A point charge +q is placed at the centre of a cube of side L. The electric flux emerging from the cube is

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

• zero

• $\frac{6{\mathrm{qL}}^2}{{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{6{\mathrm{L}}^2{\mathrm{\epsilon }}_0}$