Course Content
Class 12th Physics Chapter 1 Electric Charges And Fields
NCERT Solutions for Chapter 1 for Class 12 Physics talks about factors and topics related to Electric Charge and Fields. Some of the prominent topics covered in the Chapter are Conductors And Insulators, Charging By Induction, Basic Properties Of Electric Charge, Coulomb’s Law, etc.
Class 12th Physics Chapter 2 Electrostatic Potential And Capacitance
NCERT Solutions for Chapter 2 for Class 12 Physics talks about Electrostatic Potential in detail. The chapter revolves around relevant topics such as Potential Due To A Point Charge, Potential Due To An Electric Dipole, Potential Due To A System Of Charges, Equipotential Surfaces, etc.
Class 12th Physics Chapter 3 Current Electricity
NCERT Solutions for Chapter 3 for Class 12 Physics is an important chapter from weightage point of view. This chapter is very scoring and can be a very interesting chapter for students. The chapter talks about Electric Current, Ohm’s Law, Drift Of Electrons And The Origin Of Resistivity, Limitations Of Ohm’s Law, Resistivity Of Various Materials, etc.
Class 12th Physics Chapter 4 Moving Charges And Magnetism
Chapter 4 for Class 12 Physics can be a very scoring chapter for Class 12 students. However, it is equally complex to understand. It talks about Magnetic Force, Motion In A Magnetic Field, Motion In Combined Electric And Magnetic Fields, etc.
Class 12th Physics Chapter 5 Magnetism And Matter
NCERT Solutions for Chapter 5 for Class 12 Physics talk about topics related to Magnetism and Matter such as the Bar Magnet, Magnetic field lines, The electrostatic analogue, Magnetism And Gauss’s Law, The Earth’s Magnetism, Magnetic declination and dip, Magnetic Properties Of Materials, Diamagnetism, Paramagnetism, Ferromagnetism.
Class 12th Physics Chapter 6 Electromagnetic Induction
A very interesting and Chapter, this one in particular talks about The Experiments Of Faraday And Henry, Magnetic Flux, Faraday’s Law Of Induction, Lenz’s Law and Conservation Of Energy.
Class 12th Physics Chapter 7 Alternating Current
NCERT Solutions for Chapter 7 for Class 12 Physics talk about Ac Voltage Applied To A Resistor, Phasor-diagram solution, Analytical solution, Resonance, Oscillations, and Transformers.
Class 12th Physics Chapter 8 Electromagnetic Waves
In this chapter students will learn about Displacement Current, Electromagnetic Waves, Sources of electromagnetic waves and other such topics related to Electromagnetic Waves.
Class 12th Physics Chapter 9 Ray Optics and Optical Instruments
NCERT Solutions for Chapter 9 for Class 12 Physics talks about Reflection Of Light By Spherical Mirrors, Refraction, Total Internal Reflection and other topics related to Ray Optics.
Class 12th Physics Chapter 10 Wave Optics
NCERT Solutions for Chapter 10 for Class 12 Physics talk about Huygens Principle, Refraction and Reflection Of Plane Waves Using Huygens Principle, Refraction Of A Plane Wave, Refraction At A Rarer Medium etc.
Class 12th Physics Chapter 11 Dual Nature Of Radiation And Matter
Chapter 11 for Class 12 Physics is a scoring chapter. If learnt the concepts thoroughly, it can help students to score high marks in their Physics exam. This chapter talks about Electron Emission, Photoelectric Effect, Hertz’s observations, Hallwachs’ and Lenard’s observations, etc.
Class 12th Physics Chapter 12 Atoms
Chapter 12 for Class 12 Physics is a very interesting yet very confusing chapter for the students. It talks about topics: Alpha-Particle Scattering and Rutherford’s Nuclear Model Of Atom, Alpha-particle trajectory, Electron orbits, Atomic Spectra etc.
Class 12th Physics Chapter 13 Nuclei
NCERT Solutions for Chapter 13 for Class 12 include all answers to the questions included in the textbook. Additionally, the solutions explain topics such as Atomic Masses And Composition Of Nucleus, Size Of The Nucleus, Mass-energy And Nuclear Binding Energy, etc in detail.
Class 12th Physics Chapter 14 Semiconductor Electronics Materials Devices And Simple Circuits
Chapter 14 for Class 12 Physics Is a very scoring and interesting chapter and revolves around topics such as Intrinsic Semiconductor, Extrinsic Semiconductor, P-n Junction, Semiconductor Diode, Application Of Junction Diode As A Rectifier etc.
Class 12th Physics Chapter 15 Communication Systems
NCERT Solutions for Chapter 15 for Class 12 Physics talks about topics related to the communication systems. The important topics are Elements Of A Communication System, Basic Terminology Used In Electronic Communication Systems, etc. This is a very interesting chapter in the Class 12 Physics textbook.
Frequently asked questions (FAQs) Related to Course
Here are some frequently asked questions (FAQs) that could be relevant for your Class 12 Physics Online Course: 1. What is the Class 12 Physics Online Course offered by Free-Education (Wisdom Academy)? Our Class 12 Physics Online Course is a comprehensive learning program designed to help students excel in their CBSE Board exams. It includes chapter-wise notes, important questions, solved and unsolved previous year question papers, video explanations, interactive classes, and more. 2. Who is the instructor for this course? The course is curated and taught by Er. Mohd Sharif, an experienced educator with over 13 years of teaching Physics. He is also the founder of Wisdom Education Academy & Free-Education.In. 3. How can I access the course materials? Once you enroll in the course, you will gain access to our online learning platform. All course materials, including notes, videos, and question papers, can be accessed from there at any time. 4. Are the notes and resources provided in downloadable formats? Yes, our chapter-wise notes and other resources are available in downloadable PDF formats. This allows you to study even when you're offline. 5. How can I ask questions or clear doubts during the course? We offer doubt clearance through online classes, where you can interact with the instructor directly and get your queries resolved. You can also use our platform's messaging system to communicate with the instructor. 6. Are there regular tests to review my preparation? Absolutely, we believe in consistent evaluation. The course includes regular review tests to gauge your understanding and track your progress. 7. Can I access the course on mobile devices? Yes, our online learning platform is mobile-friendly, allowing you to access the course materials on various devices like smartphones and tablets. 8. Are there any prerequisites for enrolling in this course? This course is designed for Class 12 students studying Physics. It's tailored to cover all topics and concepts within the Class 12 Physics curriculum. 9. How can I enroll in the Class 12 Physics Online Course? Enrolling is simple. Visit our website, navigate to the Class 12 Physics Course, and follow the enrollment instructions. 10. Is there a refund policy in case I'm not satisfied with the course? Yes, we have a refund policy in place. If you're not satisfied with the course within the first 7 days, you can request a refund according to our refund policy. 11. Can I interact with other students in the course? Yes, we encourage collaborative learning. Our platform may include discussion forums or other means for students to interact and share insights. 12. Are there any additional resources provided apart from the course materials? In addition to the course materials, we may provide supplementary resources like articles, study tips, and external references to enhance your learning experience. For any other questions or clarifications, feel free to reach out to our support team at (8750387081).
Class 12 Physics Online Course: Notes, Important Questions, and Previous Year Papers
About Lesson

Electric Charge

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.

  • Electromagnetism is the phenomenon of the interaction of electric currents or fields and magnetic fields.
  • When insulating surfaces are rubbed against each other, a static charge is developed which gets discharged after getting in contact with a conductor.
  • Only one of the two charges(or polarity) gets developed on rubbing – either positive or negative. An object becomes positively charged when it loses the loosely bound electrons to another object while rubbing. The other object gains electrons and becomes negatively charged.
  • When like charges are brought near, they repel each other. Unlike charges attract each other.
  • The charges get neutralized when the two bodies are brought in contact.
  • An example of electric charge generation through rubbing of glass rod with silk and plastic rod with silk is mentioned below:

electric charge

electric charge and field
Two types of electric charges. Positive charge – every proton has a single positive charge. Negative charge – every electron has a single negative charge.

Conductors and Insulators

Criteria Conductors Insulators
Definition Substances which allow electricity to pass through them are called conductors. Substances which do not allow electricity to pass through them are called insulators.
Electron Movement Free movement None or very low
Charge transfer Charge gets distributed over whole body once it is transferred to a conductor. Charge stays at one place when transferred to an insulator.
Examples Human body, Metals, water Plastic, wood, glass
electric charge and field
  • Semiconductors offer resistance to movement of charges which is between conductors and non-conductors.
  • The process where excess charge from a body or object goes to ground, by touching the charge carrying conducting body to earth is called earthing or grounding.

Charging By Contact:-

Charging by Contact
Charging a Neutral object by Conduction
Charging by  Contact
Charging a neutral object by Conduction
Charging by Induction
Charging by Induction

Properties of electric charge

Electric charge for a body is considered as Point charges if their size is very small in comparison to the distance between them. So the charge is considered to be concentrated at one point. Following are the properties of electric charge in terms of point charges:

  1. Additivity of charges:
  • Point charges are scalars and can be added algebraically. If q1, q2, q3, … qn, are point charges, the total charge qtot=q1+ q+ q3+ qn
  • Charges have no direction but can be positive or negative.
  1. Conservation of charges:
  • Total charge in an isolated system is always conserved. When there are many bodies in an isolated system, the charges get transferred from one body to another but the net charge of the system remains same.
  • During rubbing or natural forces, no new charge is created. The charges are either redistributed or a neutron breaks up into proton and electron of equal and opposite charge.
  1. Quantization of charges:
    • The charge is always represented in the form of, q = ne. Here n is an integer and e is the charge (- for electron and + for proton). Magnitude of e = 1.602192 X 10-19 This is called quantization of charge.
    • SI unit of charge is Coulomb (C).
    • Quantization is usually ignored at macroscopic levels (μC) because at that point, charges are taken to be continuous.

Coulomb’s Law

Coulomb’s law states that Force exerted between two point charges:

  • Is inversely proportional to square of the distance between these charges and
  • Is directly proportional to product of magnitude of the two charges
  • Acts along the line joining the two point charges.
electric charge and field
electric charges and fields

Forces between multiple charges –Superposition principle

As per the principle of superposition, the force on any charge due to a number of other charges is the vector sum of all the forces on that charge due to other charges, taken one at a time.

Force between multiple charges (superposition principle)
Superposition Principle

Electric Field

Electric field is a force produced by a charge near its surroundings. This force is exerted on other charges when brought in the vicinity of this field.

  • SI unit of electric field is N/C (Force/Charge).
  • Electric field due to a charge at a point is the force that a unit positive charge would experience if placed at that point.
  • The charge generating electric field is called source charge and the charge which experiences this field is called test charge. Practically, to keep source charge undisturbed due to the electric field of test charge, the test charge is kept infinitely small.
  • Since F(Force) is proportional to q (Charge), the electric field is independent of q but depends on r (space coordinates).
  • The electric field is symmetric in spherical coordinates.
  • The concept of Electric field is used to account for the time delay for a charged body to experience force from the field of a source charge.
Properties of Electric Field Lines
electric charge and field notes
Electric Field
Electric Fields

Electric Flux

Electric flux is the measure of flow of the electric field through a given area. Electric flux is proportional to the number of electric field lines going through a normally perpendicular surface.

  • The orientation of area element decides the amount of electric flux. Thus, the area element is a vector.
  • The vector associated with every area element of a closed surface is taken to be in the direction of the outward normal.
  • Area element vector ΔS = ΔSn̂, ΔS is magnitude of area element and n̂ is unit vectorin the direction of outward normal.
  • Electric flux, Δφ = EΔS = E ΔScosθ, θ is angle between E and ΔS.
  • Unit of electric flux is NC-1m2.
  • Total flux through a surface, φ ≈ Σ EΔS
Electric Flux
Electric Flux
Electric field
Electric Flux through plane

Electric Dipole

An electric dipole is a pair of equal and opposite point charges q and –q, separated by a distance of 2a.

  • Direction from –q to q is the direction of the dipole.
  • The mid-point of locations of –q and q is called the center of the dipole.
  • Total charge of an electric dipole is zero but since the charges are separated by some distance the electric field do not cancel out.
  • Dipole moment is the mathematical product of the separation of the ends of a dipole and the magnitude of the charges (2a x q).
  • Some molecules like H2O, have permanent dipole moment as their charges do not coincide. These molecules are called polar molecules.
  • Permanent dipoles have a dipole moment irrespective of any external Electric field.
Electric Dipole
Electric Dipole

Electric field of an electric dipole

Electric field of an electric dipole at a point in space depends upon the position of the point.

  • The dipole field at a point is inversely proportional to the cube of distance from the center to the point.
  • For a very small dipole, the 2a approaches zero. This is called point dipole.

Dipole in a uniform electric field

When two charges in a dipole are separated by some distance, the forces acting at different points result in torque on the dipole.

The torque tries to align the dipole with electric field. Once aligned, the torque becomes 0.

  • Magnitude of torque = qE x 2a sinθ = 2qaE sinθ = pEsinθ.
  • Direction of the torque= normal to the plane coming outwards.
Electric Charge and fields

Continuous Charge Distribution

Type of charge distribution Denoted by Value Unit
Line Charge λ (Line charge density) ΔQ/Δl, Δl is small line element of wire that contains microscopic charged constituents and ΔQ is charge contained in the line element. C/m
Surface Charge σ (surface charge density) ΔQ/ΔS, ΔSis an area element on the surface of a conductor and ΔQ is charge on that element. C/m2
Volume Charge ρ (volume charge density) ΔQ/ΔV, ΔV is a volume element which includes a large number of microscopically charged constituents and ΔQ is charge on that element. C/m3
Electric Charge and Fields

Gauss’s Law

According to Gauss’s law, the total of the electric flux out of a closed surface is equal to the charge enclosed divided by the permittivity. The total electric flux through a closed surface is zero if no charge is enclosed by the surface.

  • Gauss’s law is true for any closed surface, no matter what its shape or size.
  • The term q on the right side of Gauss’s lawincludes the sum of all charges enclosed by the surface. The charges may be located anywhere inside the surface.
  • In the situation when the surface is so chosen that there are some charges inside and some outside, the electric field [whose flux appears on the left side of Eq. (1.31)] is due to all the charges, both inside and outside S. The term q on the right side of Gauss’s law, however, represents only the total charge inside S.
  • The surface that we choose for the application of Gauss’s law is called the Gaussian surface. The Gaussian surface can pass through a continuous charge distribution.
  • Gauss’s law is useful for the calculation of the electrostatic field for a symmetric system.
  • Gauss’s law is based on the inverse square dependence on distance contained in the Coulomb’s law. Any violation of Gauss’s law will indicate departure from the inverse square law.
Gauss' Law
Electric Charge and Fields

Applications of Gauss’s Law

Field due to infinitely long straight uniformly charged wire

Field due to a uniformly charged infinitely plane sheet

Field due to a uniformly charged thin spherical shell

Application of Gauss's Law
Application of Gauss’s Law
Join the conversation
Wisdom TechSavvy Academy