Electricity is an essential aspect of modern life, powering our homes, industries, and technology. At the heart of this phenomenon lies the concept of electric charge. In this article, we will explore the fundamentals of electric charge based on the Class XII NCERT (National Council of Educational Research and Training) book. By the end of this review, readers will gain a comprehensive understanding of electric charge, its properties, and its relevance in various applications.
Coulomb's Law:
The Class XII NCERT book discusses Coulomb's law, which describes the force between two electrically charged particles. The force is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.
Conductors and Insulators:
The concept of conductors and insulators is crucial in understanding how electric charge behaves in different materials. Conductors allow electric charge to move freely through them, while insulators do not allow easy movement of charges. This distinction plays a vital role in designing electrical circuits and devices.
Charging by Induction and Conduction:
The Class XII NCERT book covers two primary methods of charging objects - induction and conduction. Induction involves rearranging the electric charges within an object without direct contact, while conduction involves the transfer of charges through direct contact with another charged object.
Electric Field:
Electric charges create an electric field around them. The Class XII NCERT book explains how electric fields exert forces on other charges placed within their influence. The direction and strength of the electric field are governed by the nature and distribution of charges.
Electric Potential and Potential Difference:
Electric potential is the electric potential energy per unit charge at a point in space. It is analogous to gravitational potential energy. The difference in electric potential between two points is called the electric potential difference or voltage. The unit of electric potential is the volt (V).
Capacitors and Capacitance:
Capacitors are devices that store electric charge. The Class XII NCERT book introduces the concept of capacitance, which measures the ability of a capacitor to store charge. It depends on the geometry and material of the capacitor.
Conclusion:
Electric charge is a fundamental concept in physics that underpins the study of electricity and magnetism. The Class XII NCERT book provides a solid foundation for understanding the principles of electric charge, its behavior in various materials, and its applications in technology. By grasping these concepts, one can appreciate the significance of electricity in our daily lives and its role in shaping the modern world.
What is Electric Charge?
Electric charge is an intrinsic property of matter. It refers to the presence of electrically charged particles, either positive or negative, within an object. The two types of charge are attributed to protons (positive charge) and electrons (negative charge) - the fundamental particles that make up atoms.
Conservation of Electric Charge:
According to the principle of conservation of electric charge, the total electric charge of an isolated system remains constant. This means that charge cannot be created or destroyed but can only be transferred from one object to another.
FAQs on Electric Charge
Q: (a) Explain the meaning of the statement ‘electric charge of a body is quantised’.(b) Why can one ignore quantisation of electric charge when dealing with macroscopic i.e., large scale charges?
A: Electric charge of a body is quantized, this means that only integers (1,2,3,….n) number of electrons can be transferred from one body to the other. Charges are not transferred in fraction. Hence, a body possesses total charge only in integers.
(b) In macroscopic i.e. large scale charges, the charges used are huge as compared to the electric charge of electrons or protons. Therefore, it is ignored and it is considered that electric charge is continuous.
Q: When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.
A: When two bodies are rubbed against each other, it produces charges of equal magnitude in both the bodies but of opposite in nature. Hence the net charges of the two bodies are zero. When a glass rod is rubbed with a silk cloth, similar phenomena occur. This is as per the law of conservation of energy
Q: Four point charges ?? = 2 μC, ??= –5 μC, ??= 2 μC, and ??= –5 μC are located at the corners of a square ABCD of side 10 cm. What is the force on a charge of 1 μC placed at the centre of the square?
A:
In the adjoining figure ABCD is a square with sides AB = BC = CD = DA = 10 cm
Diagonals, AC = BD = √102 + 102 = 10√2 cm
AO = OC = DO = BO = 5√2 cm
At the centre of the square ABCD, O, a charge of 1 ?C.
The force of repulsion between the charges placed at A and at O is equal in magnitude but opposite in direction between the charges placed at point C and centre O. Similarly the force of attraction between the charges placed at B & O and D & O will be equal in magnitude but opposite in direction. These charges will cancel each other. Hence, the net charge at centre O will be zero
Q (a) An electrostatic field line is a continuous curve. That is, a field line cannot have sudden breaks. Why not? (b) Explain why two field lines never cross each other at any point?
A: (a) An electrostatic field line is a continuous curve because a charge experiences a continuous force when traced in an electrostatic field. The field line cannot have sudden breaks because the charge moves continuously and does not jump from one point to another.
(b) The electric field intensity will show two directions at that point where two filed lines crosses. This is not possible. Hence they do not cross.
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