Studying Physics Topics can lead to exciting new discoveries and technological advancements.
What is the Frictional electricity? Briefly Describe the Electronic Theory of Frictional Electricity.
Electronic theory accounts for the source of charge. This is based on the electronic structure of matter. We know that atoms are made up of a positively charged central core called nucleus, around which negatively charged electrons rotate in various closed orbits [Figure], The nucleus contains positively charged protons. The number of electrons in an atom is equal to the number of protons in the nucleus. As a whole an atom is electri-cally neutral.
The nucleus of an atom attracts the electrons towards it. Elec-trons lying in the outermost orbit are rather loosely bound and hence are easy to detach. If one or more electrons be somehow removed from the atom, the atom becomes positively charged. Conversely, if an atom is given one or more elec-trons, it becomes negatively charged. Therefore, a positively charged body has a deficiency of electrons in its atoms and a negatively charged body has excess electrons in its atoms. This is the electronic theory. Note that electrons alone are responsible for the electrification of a body and not the protons, because protons are firmly held in the nucleus.
An atom is composed of three fundamental particles—electron, proton, and neutron. The number of these fundamental parti-cles obviously varies from element to element. The mass of an electron is 9 × 10-31 kg and the amount of charge in it is 1.6 × 10-19C. This is the smallest possible amount of charge identified in nature and hence is taken as the unit of charge.
i. The mass of a positively charged body is less than the mass of the same electrically neutral body.
In this case, lost mass of the body = number of electrons lost by the body × mass of an electron.
ii. The mass of a negatively charged body is greater than the mass of the same electrically neutral body.
In this case, gained mass of the body = number of electrons gained by the body × mass of an electron.
Quantisation Of charge: The charge carried by a body is always an integral multiple of the smallest unit of charge which is the charge of an electron. This is known as the quanti-sation of charge.
That’s why, charge q = ±ne, where, e = charge of an electron and n = 1, 2, 3,……… a natural number. Electric charge is a scalar quantity. The net charge of a body is the algebraic sum of all the charges present.
Invariance relative to the frame of reference: The amount of a charge is independent of its state of rest or of motion; also independent of the state of rest or of motion of the observer. This is expressed by saying that an amount of charge is invariant with respect to the frame of reference.
So we can say, qrest = qmoving
Explanation of Frictional Electricity on the Basis of Electronic Theory
The electrons are bound to an atom due to the attraction of the positively charged nucleus. This attraction is obviously not equal for the atoms of different substances. So during rubbing between two bodies, some electrons are transferred from one to the other, producing equal and opposite charges simultaneously.
As for example, when a glass rod is rubbed with silk, some elec-trons from glass migrate to silk. The force of attraction between the electrons and the nucleus in glass being less than that with a in silk. Hence the glass rod becomes positively charged with a deficit of electrons and the silk becomes negatively charged with an excess of electrons.
Principle of conservation of electric charge: It states that the algebraic sum of the positive and the negative charges in an isolated system is constant. The electronic theory clearly indicates that electric charge can neither be generated nor be destroyed. It is only redistributed when electrons migrate from one body to another.
It should be mentioned that the principle had been known, long before the invention of electron and proton. Till date, no devia-tion has been observed for this principle.
The principle of conservation of charge is a universal law—no physical phenomenon exists for which this law is violated.