Electrostatic Induction

Description:

We know that In case of a metal containing positive and negative charges in equal numbers, the net charge in the atom is 0. This is possible only when the temperature is 0 Kelvin (i.e -273 degree Celsius). At this low temperature, the energy contained by electron is so small that it can not leave the orbit.

On increasing the temperature (say at room temperature i.e. 300 Kelvin) the electrons in the atom  acquire a high energy such that some of the electrons leaves the atom making the atom positively charged. But the system as a whole remains neutral. (with positively charged atom and negatively charged electrons).

Whenever we take a body it is having positive and negative charged particles in equal number, so that net charge on the body remains zero. Assuming that these charges are moving randomly in the body.

Now, if an excess positively charged glass is taken near to the neutral body, the positive charges in the glass, according to its nature will repel all the positive charges of the body thereby shifting most of the positive charges at the farther corner which is away from positively charged glass and attract all the negative charges, thereby shifting most of the negative charges to the corner which is nearer to positively charged glass.In this way the particle of different nature assembling at different corners is called polarization of charges.

This phenomenon in which the free charges in conductor gets polarized is called induction.

A neutral body with zero charge can apply force on a charged body.

Due to electrostatic induction  the neutral body gets attracted towards the charged glass.

The distance between the polarized negative charges and positive charged glass rod is less so the force of attraction between them will be more.

Whereas, the distance between the polarized positive charges and positive charged glass rod is more so the force of repulsion between them will be less. Hence net force is attraction.

Note − In a neutral body there is always an induction before attraction. So it can be said induction preceeds attraction.