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Full Chapter Class 12 Current Electricity as per NCERT 2025

CBSE Class 12 Class 12 Physics Chapter 3:

CBSE Notes of Class 12 for Chapter 3 Current Electricity provides a detailed overview of the fundamental concepts related to electric current and the principles governing its flow through conductors.

These notes have been carefully made by the teachers at MKC Prayagraj (Major Kalshi Classes) to help Class 12 students understand the topics clearly and prepare well for their exams.

This chapter covers important topics such as Ohm's Law, which explains the relationship between voltage, current, and resistance in a circuit. It also includes the concepts of resistivity, conductivity, and the temperature dependence of resistance. 

These notes are designed to help students understand the intricacies of current electricity, preparing them for both theoretical and practical aspects of the subject.

Current Electricity Overview

CBSE Class 12 Physics Notes for Chapter 3 Current Electricity  have been prepared by subject experts of MKC. These notes cover the basics of electric current, Ohm's Law, resistivity, and conductivity, as well as how temperature affects resistance. 

They also explain how resistors work in series and parallel, and how to use Kirchhoff's laws to solve complex circuits. These notes are designed to make difficult topics easier to understand, making them a valuable resource for students learning about current electricity.

CBSE Class 12 Physics Notes Chapter 3 PDF

CBSE Class 12 Physics Notes for Chapter 3 Current Electricity are available for download in PDF format through the link provided below. These notes are designed to help students grasp key concepts such as electric current, Ohm's Law, and circuit analysis. 

With clear explanations and practical examples these notes are a great resource for thorough preparation. Download the PDF to access detailed explanations and enhance your understanding of current electricity.

CBSE Class 12 Physics Notes Chapter 3 Current Electricity PDF

Physics Notes Chapter 3 Current Electricity

Here are important notes for Class 12 students on CBSE Physics Chapter 3 Current Electricity. This chapter explains the basics of electric current which is the flow of electric charge through a conductor.

It also covers current carriers like electrons in metals and ions in solutions that move to create the current. The chapter talks about drift velocity which is the average speed of these carriers when an electric field is applied. 

You’ll also learn about Ohm's Law, Kirchhoff’s Rules and how resistors work in circuits. These notes are helpful for understanding how electricity flows in circuits.

Electric Current

Electric current is the flow of electric charge through a conductor. In most cases, this charge is carried by electrons moving through a wire or other conductive material. The amount of electric charge that flows through a conductor per unit time is defined as the current which is represented by the symbol II I.

It is important to note that electric current is considered a scalar quantity . Even though it has a direction (from positive to negative terminal), it is not a vector because it does not follow the rules of vector addition.

Current Carriers

Current carriers are the charged particles that move through a conductor to create an electric current. Depending on the type of material (solid, liquid, or gas), the nature of these current carriers can vary:

In Solids :

The most common current carriers in solids, especially metals, are electrons . In metallic conductors, free electrons move through the lattice of positive ions when an electric field is applied, resulting in a current.

Metals have a large number of free electrons that are not bound to any particular atom, allowing them to move easily through the material.

In Liquids :

In liquids, the current is carried by ions . When an electric field is applied, positive ions (cations) move towards the negative electrode (cathode), and negative ions (anions) move towards the positive electrode (anode).

This movement of ions constitutes an electric current. An example of this is the conduction of electricity in saltwater or any other electrolyte solution.

In Gases :

In gases, current carriers are a mix of electrons and ions . Normally, gases are poor conductors, but under certain conditions (like high voltage), they can become ionized.

In ionized gases, free electrons and ions move under the influence of an electric field, resulting in a current. This phenomenon is commonly seen in neon signs or lightning.

Drift Velocity

Drift velocity is the average velocity that a charged particle, such as an electron, attains due to an electric field applied across a conductor. It represents the net motion of charge carriers in a conductor when an electric field is applied. 

Drift velocity is different from the random thermal velocity of the particles, which is much higher.

Ohm’s Law

Ohm’s Law is a fundamental principle in electrical engineering and physics that relates the voltage, current, and resistance in an electrical circuit. It states that the current through a conductor between two points is directly proportional to the voltage across the two points, provided the temperature remains constant.

Drawbacks of Ohm’s Law

While Ohm's Law is widely applicable, it has certain limitations and does not apply to all materials and situations:

Non-Linear V-I Relationship : Ohm's Law assumes a linear relationship between voltage and current. If the relationship between V and I is non-linear, Ohm's Law does not apply. This nonlinearity can occur in devices like diodes and transistors, where the resistance changes with the voltage or current.

Dependence on Voltage Sign : In some materials and devices, the relationship between current and voltage can depend on the sign of the voltage. For example, certain semiconductor devices may exhibit different behaviors when the polarity of the applied voltage changes, leading to a non-Ohmic behavior.

Non-Unique Relation : Ohm's Law implies a unique resistance for a given conductor. However, in practical scenarios, the resistance can vary with factors like temperature, frequency of the applied voltage, and the presence of impurities. This makes the relation between current and voltage non-unique in some cases.

Electrical Resistance

Electrical Resistance is a measure of how much a material opposes the flow of electric current. It quantifies how difficult it is for electric charge to pass through a conductor

or component. Understanding electrical resistance is crucial for analyzing and designing electrical circuits.

Colour Code for Carbon Resistors

Colour Code for Carbon Resistors is a system used to identify the value of a resistor through a series of coloured bands printed on its body. 

Each colour represents a specific digit or multiplier, and the combination of these colours gives the resistance value of the resistor. This code system simplifies the process of reading resistor values without needing to measure them directly.

Here is a overview of how the colour code works:

First Band : Represents the first significant digit of the resistor value.

Second Band : Represents the second significant digit.

Third Band : Represents the multiplier (which tells you the power of ten by which the combined digits should be multiplied).

Fourth Band (if present) : Represents the tolerance, which indicates how much the actual resistance might vary from the stated value.

What Are Kirchhoff’s Rules?

Kirchhoff’s Rules are fundamental principles used to analyze electrical circuits. They are important for solving complex circuits involving multiple resistors, power sources, and other components. There are two primary rules:

1. Kirchhoff’s Voltage Law (KVL)

Statement : The algebraic sum of all the voltages around any closed loop in a circuit is zero.

Explanation : KVL is based on the conservation of energy. In a closed circuit loop, the total amount of energy gained from voltage sources (like batteries) must be equal to the total amount of energy lost in resistive elements (like resistors). Therefore, when you sum up all the voltage rises and drops around a loop, they must add up to zero.

2. Kirchhoff’s Current Law (KCL)

Statement : The sum of currents entering a junction (or node) in a circuit is equal to the sum of currents leaving the junction.

Explanation : KCL is based on the principle of conservation of electric charge. At any electrical junction, the amount of current flowing into the junction must equal the amount of current flowing out. This ensures that charge is neither created nor destroyed at the junction.

Potentiometer

A potentiometer is a versatile electrical device used to measure and compare potential differences (voltages) with high accuracy. It operates based on the principle of measuring voltage by balancing it against a known reference voltage.

Combination of resistors

Resistors are objects used to restrict the flow of charges in any conductor. However, these individual resistors can be arranged in different patterns to obtain different results. Resistors can be connected in 2 main ways:

In series

In parallel

Resistors in parallel

Resistors in parallel means when resistors are connected one below the other. All ends are connected to a common junction.

The above image shows that four resistors, R1, R2, R3, and R4, are connected in parallel. A potential difference V is applied at its ends.

Some important properties

Equivalent resistance R is

1/R = 1/R1 + 1/R2 + 1/R3 + 1/R4

The potential difference across each resistor is the same.

The electric current ‘I’ drawn from the source equals the sum of currents flowing through individual currents.

I = I1 + I2 + I3 + I4

Benefits of CBSE Class 12 Physics Notes Chapter 3 Current Electricity

Comprehensive Understanding : The notes provide a thorough explanation of key concepts in current electricity, such as electric current, drift velocity, Ohm’s Law, electrical resistance, and more. This comprehensive coverage helps students grasp fundamental principles clearly.

Clarity on Core Concepts : Topics like electric current, current carriers, and drift velocity are explained in a detailed yet easy-to-understand manner, making complex concepts more accessible to students.

Detailed Examples : The notes include detailed examples and problems, which help students apply theoretical concepts to practical situations, enhancing their problem-solving skills.

Key Formulas and Definitions : Important formulas, definitions, and laws such as Kirchhoff’s laws and Ohm’s Law are highlighted, providing quick reference points for study and revision.

Exam Preparation : The notes are structured to align with the CBSE curriculum, making them an excellent resource for exam preparation. They include common questions and answers that are likely to appear in exams.

Application of Concepts : The section on the colour code for carbon resistors and resistor combinations helps students understand practical applications and real-life uses of current electricity concepts.

Concept Reinforcement : By covering topics like current density, conductance, and electrical conductivity in detail, the notes reinforce students' understanding and provide a solid foundation for more advanced studies in physics.

Current Electricity Class 12 | NCERT Solutions & Full Chapter Guide

Struggling with Class 12 Physics Chapter. Current Electricity? You're not alone. This chapter is concept-heavy and crucial for scoring in CBSE Boards, JEE, NEET, and NDA. But don't worry. MKC (Major Kalshi Classes) has made it easy for you!

What You’ll Get in MKC's Full Chapter Guide:

NCERT-based Notes & Solutions by expert faculty

Step-by-step breakdown 

Solved numerical examples & past year questions

Quick revision tips & visual concept explanations

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Watch on YouTube. Complete Chapter Explanation

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FAQ

Q1. What is electric current and how is it measured?

Ans: Electric current is the flow of electric charge through a conductor, typically carried by electrons. It is measured in amperes (A) and represented by the symbol I. The formula is:

I=QtI = \frac{Q}{t}I=tQ​

Where Q = charge (in coulombs), t = time (in seconds).

Q2. What is Ohm’s Law?

Ans: Ohm’s Law states that the current (I) passing through a conductor between two points is directly proportional to the voltage (V) across the two points, provided temperature remains constant.

V=IRV = IRV=IR

Where R is the resistance in ohms (Ω).

Q3. What are the limitations of Ohm’s Law?

Ans:

Not applicable to non-ohmic devices like diodes and transistors.

Fails when the temperature of the conductor changes.

Not valid if the V-I relationship is non-linear.

Q4. What is drift velocity?

Ans: Drift velocity is the average velocity acquired by charge carriers (like electrons) in a conductor under the influence of an electric field. It is typically very small.

Q5. What is the difference between conductance and conductivity?

Ans:

Conductance (G) is the reciprocal of resistance: G=1RG = \frac{1}{R}G=R1​

Conductivity (σ) is a material property that describes how well a material conducts electricity. It is the reciprocal of resistivity.

Q6. What are Kirchhoff’s Rules?

Ans:

Kirchhoff’s Current Law (KCL): The sum of currents entering a junction equals the sum leaving it.

Kirchhoff’s Voltage Law (KVL): The sum of potential differences around any closed loop in a circuit is zero.

Q7. What is the colour code for carbon resistors?

Ans: Carbon resistors use coloured bands to represent resistance values.

1st & 2nd bands: Significant digits

3rd band: Multiplier

4th band: Tolerance Example: Red (2), Violet (7), Orange (×1000), Gold (±5%)

Q8. How are resistors connected in series and parallel?

Ans:

Series: Req=R1+R2+R3+...R_{eq} = R_1 + R_2 + R_3 + ...Req​=R1​+R2​+R3​+... Same current flows through all resistors.

Parallel: 1Req=1R1+1R2+...\frac{1}{R_{eq}} = \frac{1}{R_1} + \frac{1}{R_2} + ...Req​1​=R1​1​+R2​1​+...

Voltage across each resistor is the same.

Q9. What are current carriers in different states of matter?

Ans:

Solids (metals): Free electrons

Liquids: Ions (cations and anions)

Gases: Electrons and ions (only when ionized)

Q10. What is a potentiometer and its application?

Ans: A potentiometer is an instrument used to measure potential differences accurately by balancing them against a known voltage. It is commonly used in comparing emf of cells and calibrating voltmeters.

Q11. Why is electric current considered a scalar quantity?

Ans: Despite having a direction, electric current is considered scalar because it does not follow vector addition laws and only magnitude matters in calculations.

Q12. What is the unit of resistivity and conductivity?

Ans:

Resistivity (ρ): ohm-meter (Ω·m)

Conductivity (σ): siemens per meter (S/m)

Q13. How does temperature affect resistance?

Ans: In most conductors, resistance increases with temperature due to increased collision of electrons. In semiconductors, resistance typically decreases with temperature.

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Class 11 Physics | MOTION IN ONE DIMENSION (5) | JEE Main PYQs | JEE, CUET, BITSAT, WBJEE Prep

Welcome to another power-packed session of Class 11 Physics – Motion in One Dimension (Part 5) with a focus on JEE Main Previous Year Questions (PYQs) and other competitive exams like CUET, BITSAT, WBJEE, and State Boards. 🚀

In this video, we dive deeper into solving high-quality questions that test your understanding of concepts like displacement, velocity, acceleration, relative motion, and equations of motion — all under the umbrella of motion in a straight line. 🧠📈

Understanding Motion in One Dimension is foundational for mastering advanced topics in kinematics and mechanics. That’s why this session not only helps in cracking entrance exams but also strengthens your base for board-level physics. 💪

🔍 What you’ll learn in this video:

How to approach and solve JEE Main-level problems with smart techniques

Concept clarification through visual and logical explanations

Application of motion equations and graphical analysis

Tips to avoid common mistakes in competitive exams

Whether you're a JEE aspirant or preparing for your Class 11 exams, this video is tailored to provide maximum value in minimum time. It includes step-by-step solutions to actual PYQs, helping you develop a problem-solving mindset crucial for high scores. ✅

💡 Ideal for:

JEE Mains/Advanced Aspirants

CUET & BITSAT Candidates

WBJEE & VITEEE Prep

CBSE and State Board Students

🔥 Don’t forget to watch till the end for bonus tips and time-saving strategies that can truly make a difference in your exam performance.

📌 Watch Now: 👉 https://youtu.be/QwmSyAsnEjY?si=8kcD-bglxTgCyg8B

🔔 Subscribe to @sethiswiftlearn for more PYQ practice, conceptual videos, and exam hacks.

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Things you should not do in IIT JEE 2020 Preparation

Situation are not the same like always things are changing drastically. Now the (NTA) National Testing Agency will conduct the JEE (Main)-2020 Examination twice for admission to Undergraduate Programs in NITs, IIITs and other Centrally Funded Technical Institutions (CFTIs), etc. in the next academic year (2020-2021).

Attention JEE Aspirants! Here are the top 8 things you should not do in IIT JEE 2020 Preparation

1.)Omit  the basics No matter you study online for IIT JEE or refer some reference books available in the market if you dnt know the basic block knowlege than craking tha exam can be hard for you.

2) delaying tactics

procrastination / delaying tactics is the thief of time — if you delay doing something, it will take longer to do later on. most of you might think that you will begin preparation tomorrow but that tomorrow never comes. They often get forced behind in their preparation. JEE/NEET preparation gets hampered due to this wasted time. The cause may be a lack of motivation. It’s frustrating. And as time passes, the only thing that seems to change is the hour on the clock. It’s okay sometimes to miss the daily study schedule, you can cover that during the week. But what’s not good is staring at your books, daydreaming, and doing nothing. solution is making a to-do list for the month, week or day, rewarding yourself after a study session.

3) neclecting health issues

They stay up late and study, do not take proper meals and many times become too strict to follow the study schedule. 4) No Timetable

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Electrostatics | JEE Main PYQs | JEE Mains, Neet, CUET Prep

Electrostatics is one of the most crucial topics in Class 12 Physics, forming the foundation for various competitive exams like JEE Mains, NEET, and CUET. Understanding electrostatics is essential for solving numerical problems, conceptual questions, and practical applications in physics. This session will cover previous year questions (PYQs) from JEE Main, ensuring you get a thorough grasp of the topic with problem-solving techniques.

🔗 Watch the full video here: Electrostatics | JEE Main PYQs

What You Will Learn in This Session?

Basic Concepts of Electrostatics: Understanding electric charges, Coulomb’s law, and the principle of superposition.

Electric Field & Potential: Learning about electric field lines, electric dipole, Gauss’s law, and potential energy.

Capacitance & Capacitors: Explanation of parallel plate capacitors, series & parallel combinations, and energy stored in a capacitor.

Previous Year Questions (PYQs): Solving JEE Main, NEET, and CUET level problems with step-by-step explanations.

Short Tricks & Problem-Solving Strategies: Time-saving tips to solve electrostatics problems efficiently.

Why is Electrostatics Important for JEE, NEET & CUET?

Electrostatics covers a significant weightage in the JEE Main & Advanced syllabus.

NEET aspirants require a strong foundation in electrostatics for medical entrance exams.

CUET candidates need to understand electrostatic applications in real-world physics.

Who Should Watch This?

✔️ JEE Aspirants looking for PYQ practice to improve problem-solving skills. ✔️ NEET Students aiming to strengthen their understanding of electric charges & fields. ✔️ CUET Candidates needing in-depth clarity on electrostatics fundamentals.

Boost Your Exam Preparation with This Session!

🔹 Learn concepts with practical examples 🔹 Master shortcut techniques to solve questions faster 🔹 Revise previous year JEE Main PYQs effectively 🔹 Clear your doubts with detailed explanations

📌 Don’t miss out on this opportunity to strengthen your electrostatics concepts! 🔥 Watch Now: Click Here