Electric Charge...

Which of the following is false for electric lines of force ?

There are two charges +2 $$\mu C$$ and -3$$\mu C$$ .The ratio of forces acting on them will be 

If the surface normal vector $$  \hat{n}  $$ makes an angle $$  \theta  $$ withthe electric field $$  \vec{E}  $$ , then the electric flux through asurface of area $$  d S  $$ is given by

An electric field exists in the space between two charged metal plates.
which graph shows the variation of electric field strenth E with distance d from X along the line XY ?

A charge q is placed at the center of the  line joining two equal charges Q . The system of the three charges will be equilibrium, If q is equal to :-

A problem of practical interest is to make a beam of electrons turn at $$90^{\circ}$$ corner. This can be done with the parallel plates shown in figure. An electron with kinetic energy $$8.0\times 10^{-17} J$$ enters through a small hole in the bottom plate. The strength of electric field that is needed if the electron is to emerge from an exit hole $$1.0\ cm$$ away from the entrance hole, traveling at right angles to its original direction is _______ $$\times 10^{5} N/C$$.

The flux through the hemispherical surface in the figure shown below is

There are three concentric thin sphere of radius a, b, c ( a > b > c ) . the total surface charges densities on their surfaces are $$ \sigma , - \sigma , \ sigma $$ respectively. the magnitude of electric field at r ( distance from centre ) such that a > r > b is :

Two charges of equal magnitudes and at a distance $$r$$ exert a force $$F$$ on each other. If the charges are halved and the distance between them is doubled, then the new force acting on each charge is

A charged oil drop is suspended in a uniform field of 3 x 10⁴  v/m so that it neither falls nor rises. The charge on the drop will (Take the mass of the charge  = 9.9 x 10^-15 kg  and g = 10 m/s²  )