Modern Theory of Electrification

Electrostatics

The branch of physics which deals with statical frictional electrically is called electrostatics.In electrostatics,electric charges are produced to friction between two bodies due to the transfer of electrons from one body to another without their actual moment .so,a charge can be neutral due to friction.

Electric Charge

Electric charge is the intrinsic property of a matter due to which it produces and experiences electrical and magnetic effects.When a glass rod is rubbed with silk and brought near small paper pieces it attracts them. The property that is developed in glass rod on rubbing with silk is supposed to be positive charge and that developed in silk is supposed to be the negative charge.

Work Function

The maximum energy required to remove an electron from an atom is called work function. Smaller the work function easier will be the removal of electron and vice-versa. Metals have a low value of work function and that for non-metal is high.

Modern theory of electrification

The process of developing charge in a body is called electrification. According to this theory, a body can be charged by the transfer of electrons.Every material is composed of atoms. In an atom, the number of positivity charged protons must be equal to the number of negatively charged electrons. So, it is electrically neutral. By any process, if some of the electrons are removed, the body becomes positively charged because of a number of protons than electrons. On the other hand, the material that receives electrons acquires negative charge because of extra electrons added.

Properties of Electric Charge

1. The charge is a scalar quantity, so, it doesn't obey vector law of algebra.
2. like charges repel each other but unlike charges attract each other.
3. The charge follows conservation principle i.e. the total charge of an isolated system remains constant. This means charge can be neither created nor destroyed but transferred from one body to another.
4. The charge is always in the form of an integral multiple of electronic charge and never it’s fraction. This is known as quantization of charge.\(\text{i.e.} q = \pm ne\) where, n is integer and \( e = 1.6 \times 10^{-19}\)
5. Accelerated charge radiates energy.
6. Charge resides on the outer surface of the conductor.

Methods of Charging a Body

An object can be electrified by different methods as given below:

1. By friction

When a body is rubbed with another suitable pair give and take of electrons occurs and the bodies becomes charged. The body that loose electrons acquire a positive charge and another that receives electrons possesses a negative charge. Example: glass, fur etc.

2. By conduction

When a neutral body is brought into contact with a charged body some charges flows into it and becomes charged. The charged acquired by the neutral body is similar to that of the charged body.

3. By induction

The process of development of electric charge at the two winds of an isolated conductor. When a charged body is brought near one end of the conductor is called electrostatic induction. The charge developed at near ends is called induced bound charge is called induced a free charge.

The process of temporary electrification of an initially uncharged conducting body by bringing a charged body close to it but not making actual contact is known as charging by induction.

Inducing and Induced charge

The charge present in a charged body that induces charges in another uncharged body is called inducing a charge.The charge developed in an initially uncharged conducting body by a bringing a charged body close to it but not making actual contact is known as induced charge. These are two types:

1. Bound charge
   The charges developed at the end closer to the inducing charge are known as a bound charge. They are called so because they are strongly held by the attractive force of the insulating stand.
2. Free charge
   The charge developed at the far end to the inducing charges is known as a free charge. They are called so because they can freely flow if they are provided any conducting path.

Conductors and Insulators

The substances which can conduct electricity through them easily are called conductor for example silver,gold,copper,human body,earth etc.Such substances have sufficient free electrons and the charges are not localized but uniformly distributed over their surfaces.

The substances which do not conduct electricity through them are called insulators for example wood,plastic,diamond,glass,paper etc.In such substances, there are not free electrons.Consequently, the electric charges are not uniformly distributed over their surfaces but localize.