Learn All Laws of Class 12 Physics Mentioned In Cbse Syllabus 2024-2025

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Read chapter-wise Physics laws like Coulomb's law, Ohm’s Law, Ampère's circuital law, Kirchhoff’s law, Gauss’s Law, etc. mentioned in class 12 NCERT books.

Learn all the important laws with the help of Class 12 Physics Syllabus for CBSE Board Exams 2024-25. Check out the complete list with chapter-wise distribution.

The laws of Physics are fundamental principles that come from observing how things work in the world around us. They help us understand and classify the way things behave.

Through systematic experimentation and analysis, scientists have uncovered patterns and regularities in the behaviour of objects and systems. These observations were then compiled in physical laws, constituting the fundamental principles governing various aspects of the universe.

For instance, Newton's laws of motion describe how objects move and interact with one another, while laws of thermodynamics elucidate the transfer of energy and the behaviour of heat in systems. These laws are not arbitrary rules imposed on nature but empirical generalizations derived from countless experiments and observations.

Class XII Physics Syllabus 2024-25 talks about some of the physics laws in concern with the chapter. Since the Class 12 CBSE Physics Syllabus is divided into two parts Part I and Part II, it gets sometimes overwhelming to go through each chapter in both books and study the laws separately. Therefore we have combined all the physics laws chapter-wise in one place to make it easier for you to revise.

Chapter-wise Important Laws: CBSE Syllabus Class 12 Physics 2025

Learn all the important  laws of physics chapter-wise:



Chapter-Name 

Important Laws

  1. Electric Charges And Fields

Coulomb's law

It describes the electrostatic force between two point charges. It states that the force between two point charges is directly proportional to the product of their magnitudes and inversely proportional to the square of the distance between them. Mathematically, Coulomb's law can be  F  = k q1q2/ r2

Where F is the electrostatic force, q1 & q2 are the magnitudes of the charges,r is the distance between them, and k is Coulomb's constant, a proportionality constant.

  1. Electrostatic Potential and Capacitance

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  1. Current Electricity

  1. Ohm’s Law


Ohm's Law describes the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit. It states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance. Mathematically, Ohm's Law is expressed as V = I 

or, V = R I


  1. Kirchhoff’s First Law or Kirchhoff’s Current Law


It states that the total current entering a junction (or node) in a circuit is equal to the total current leaving the junction. In other words, the algebraic sum of currents at any node in a circuit is zero.


∑ I in =∑I out


  1. Kirchhoff’s Second Law or Kirchhoff’s Voltage Law


It states that the sum of the voltages around any closed loop in a circuit is equal to zero. In simpler terms, the algebraic sum of the voltage rises and voltage drops in a closed loop equals zero.


∑V loops = 0

  1. Moving Charges and Magnetism



Ampère's circuital law or Ampere’s Law


It describes the relationship between the magnetic field and the electric current that produces it. Ampère's circuital law states that the magnetic field around a closed loop is directly proportional to the current passing through the loop and inversely proportional to the distance from the current-carrying conductor.


∮ B ⋅ d l =μ 0⋅I enclosed


B​ = magnetic field intensity,


dl = an infinitesimal element of length along the closed loop path,


μ0 = is the permeability of free space (a constant value),


I enclosed =  is the total current passing through any surface bounded by the closed loop.

  1. Magnetism and Matter



Gauss’s Law


This states that the total electric flux through a closed surface is equal to the total electric charge enclosed by that surface divided by the permittivity of free space.


ϕ = Q/ϵ0


Where,

Q = Total charge within the given surface

ε0 = The electric constant.

  1. Electromagnetic Induction



  1. Faraday’s Law of Induction


This states that the induced emf in a circuit is directly proportional to the rate of change of magnetic flux passing through the circuit


ε= − dΦ/dt


ε = the induced electromotive force (emf) in the circuit,

Φ = the magnetic flux through a surface bounded by the circuit,

dΦ/dt = is the rate of change of magnetic flux with respect to time.


  1. Lenz’s Law


This states that the induced current will always flow in a direction that creates a magnetic field opposing the change in the original magnetic field that caused the current. This law is a consequence of the conservation of energy principle.

  1. Alternating Current



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  1. Electromagnetic Waves



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  1. Ray Optics and Optical Instruments



Laws of Reflection


  1. First Law


When light strikes a surface the incident ray, the reflected ray, and the normal (a line perpendicular to the surface) all lie in the same plane.


  1. Second Law

This law states that the angle of reflection is always equal to the angle of reflection


Angle of reflection =Angle of Incidence

  1. Wave Optics



Huygens' Principle


This principle states that every point on a wavefront can be considered a source of secondary wavelets that spread out in all directions at the same speed as the wave itself. The new wavefront at any instant is the envelope of these secondary wavelets.

  1. Dual Nature of Radiation and Matter

-

  1. Atoms



-

  1. Nuclei




Radioactive Decay Law

The radioactive decay law states that the rate at which nuclei of a radioactive substance decay per unit time is directly proportional to the total number of nuclei present in the sample material. It is represented mathematically as 


ΔN/Δt ∝ N

Where,

N =  the total number of nuclei in the sample 

ΔN = number of nuclei that undergoes decay

Δt=unit time

  1. Semiconductor electronics:

Materials, Devices,

And Simple Circuits

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CBSE  Class 12 Physics Syllabus

We have provided all the important laws covered in 12th Class Physics Chapters in the syllabus provided by CBSE for 2025. This will help you with the quick revision of all the laws in one go. The laws mentioned above are in accordance with the latest CBSE XII Physics Syllabus Memorize the formulas provided along with each law, and practice numerical, or questions related to the laws. This will help you with a better understanding of the law and the concepts associated with it. 

 

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