Topic under the Chapter : Electrostatics
1. Short Introduction
To understand this topic, we need to know about ‘free electrons’. These free electrons behave very similar to the gas atoms in a container. Both of them are under continuous random motion throughout the space given to them.
Free electrons are nothing but some loosely bonded valence electrons which come out of the atom very easily ; just as the loosely stitched button comes out of the shirt very easily : )
Note that :
- A neutral body has equal number of positive charges and negative charges. Presence of free electrons doesn’t disturb the neutrality of the body as free electrons are also negative charges but the only difference being that ; they are free to move inside the body
2. Induction in Metal and Non-metals
When we talk of bodies, we classify them as –
- Metals – The ones in which there are a lot of free electrons
- Non-metals – electrons are bounded to the Atom tightly (Atom loves them !)
2.1 Charge Induction in Metals
Now suppose you have a metal conductor placed in a region. And you bring a positive charge ‘+q’ in that region ‘externally’.
Important Note :
- excess of electrons implies negative charge
- deficiency of electrons implies positive charge
These charges are ‘induced’ on the conductor due to the external charge. This phenomenon of separation of charges in a body by some external factor is called ‘Charge Induction’
2.2 Charge Induction in Non-Metals
As discussed, the basic difference between non-metal and metals is the absence of free electrons in case of non-metals.
Setup – Let’s consider the same condition. An non-metallic body has been placed in a region. Now, we bring a positive charge in vicinity of this body.
Important Note :
- Atom is made up of a positively charged nucleus and an negatively charged electron cloud surrounding it. In a neutral, undisturbed atom, the negative center and the positive center, both, coincide.
This alignment in dipoles in a non-conducting body due to an external charge is called induction in non-conducting bodies or ‘Polarization’. The separation between positive and negative charges is very very small. So, usually, we ignore it in our problem solving, etc.
FAQ section :
In presence of an external electric field set up by an charge placed outside a body; charge separation happens within the body. This phenomenon is called charge induction.
The formation of dipoles within the atoms of non-metal due to the external electric field set up by the charge placed outside the body is called Polarization
