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In this article, ‘Electrostatic Charges’ from Class 12 Physics is being discussed.
Electrostatic Charges 12th Physics – Electrostatics: Electrostatics is the branch of Physics which deals with the study of charges at rest. Electric charge: Electric charge is something possessed by material objects that make it possible for them to exert electrical force and to respond to electrical force. SI unit of charge is Coulomb (C). Methods of charging
There are three methods: 1. 2. 3.
a) Rubbing (charging by friction) b) Conduction c) Induction What is frictional electricity?
The charge obtained by a body on rubbing with another body is called frictional electricity. Example: When a glass rod is rubbed with silk, the glass rod gets positively charged and silk gets negatively charged. How does a body get charged? A body gets charged by the transfer of electrons. The body which loses electrons gets positively charged and the body which gains electrons gets negatively charged.
Thus, there are two types of charges: Positive charge and Negative charge.
Charging by conduction When a charged body is brought in to contact with an uncharged conductor, charge flows from the charged body to the uncharged body. Charging by induction When we bring a charged body near to an uncharged conductor (without touching), the end of the uncharged conductor which is near to the charged body gets oppositely charged and the farther end is charged with the same type of charge. For practice of Electrostatics & more, click NCERT Physics Class 12
Properties of Electric charge
Conservation Electric Charge: The total charge of an isolated system is always conserved that means charge can neither be created nor be destroyed but can be transferred from one body to another.
Additive property: The total charge of an isolated system is equal to an algebraic sum of charges on individual bodies of the system. If a system contains ‘n’ charges q1, q2, q3, ——, qn, then the total charge of the system is q1 + q2 + q3 + ——- +qn.
Charge is unaffected by motion: The charge on a body remains unaffected of the velocity e. charge at rest = charge in motion Like charges repel while unlike charges attract each other. Quantization of electric charge: The total charge on a body is integral multiple of fundamental charge ‘e’ that is
q = ne, where n is an integer and e = 1.602192 × 10-19 C Question: Repulsion is the sure test of electrification. Explain. Ans: A charged body can attract another oppositely charged body as well as an uncharged body. But a charged body can repel only similar charged bodies. So we can say that repulsion is the sure test of electrification Question: A comb run through one’s hair attracts small bits of paper. Why? What happens if the hair is wet? Ans: Because the comb gets charged by friction. If the hair is wet friction between the hair and comb reduces. So the comb does not get charged and hence not attract small bits of papers.
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