How rubbing of the two bodies produces electricity?

Define electric field at a point. An electron moves a distance of 6.0 cm when accelerated from rest by an electric field of strength \(2\times {{10}^{4}} N{{C}^{-1}}\). Calculate the times of travel.

(i) Explain, using suitable diagram,  the  difference in the behaviour of a 
(a) conductor
(b) dielectric in the presence of external electric field. Define the terms polarisation of a dielectric and write its relation with susceptibility.
(ii) A thin metallic spherical shell of radius R carries a charge Q on its surface. A point charge Q/2 is placed at its centre C and an another charge +2Q is placed outside the shell at a distance x from the centre as shown in figure. Find
(a) the force on the charge at the centre of the shell and at point A,
(b) the electric flux through the shell.

The electric field at a point on the axial line at a distance of 10 cm from the center of an electric dipole is 3.75\(\times\) N/C. Calculate the length of an electric dipole.

(i) Three equal charges, each equal to q are placed at the three corners of square of side \(\alpha \). Find the electric field at the fourth corner.
(ii) Find the electric field at the point P in figure given below.

A dipole is made up of two charges + q and - q separated by a distance 2a. Derive an expression for the electric field E\(\overrightarrow{e}\) due to this dipole at a point distance r from the centre of the dipole on the equatorial plane. Draw the shape of the graph, between |E_e| and r when r > >a.  
If this dipole were to be put in a uniform external electric field \(\overrightarrow{E}_e\) , obtain an expression for the torque acting on the dipole.

Sweta goes to physics laboratory in her practical class. Her teacher reaches late. In the mean time she notices that a student handles a circuit containing capacitor carelessly. She advises him not to handle the capacitor in such way otherwise he may get a severe shock.
(a) According to you what values are displayed by Sweta?
(b) Why does she advise him not to handle capacitor carelessly? Explain. 

(a) Define electric flux. Write its S.1.unit.
(b) A small metal sphere carrying charge +Q is located at the centre of a spherical cavity inside a large uncharged metallic spherical shell as shown in the figure. Use Gauss's law to find the expressions for the electric field at points P₁ and P₂

(c) Draw the pattern of electric field lines in this arrangement

The equivalent capacitance of the combination between A and B in the given figure is 15 \(\mu F\). Calculate the capacitance of capacitor C.