Class 12th Physics Current Electricity notes for CBSE Board

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Full notes on Class 12th Physics Chapter Current Electricity for CBSE Board:


Chapter : Current Electricity

1 Introduction

Electric current is the flow of electrons through a conductor. It is measured in amperes (A).


2 Electric Current

Electric current is defined as the rate of flow of electric charge.


Mathematically, it is represented as:


I = Q/t


where I is the electric current, Q is the electric charge, and t is the time.


3 Electric Circuit

An electric circuit is a path through which electric current flows. It consists of a conductor, a switch, and a source of emf.


4 Ohm's Law

Ohm's law states that the electric current flowing through a conductor is directly proportional to the potential difference across it, provided the temperature remains constant.


Mathematically, it is represented as:


V = IR


where V is the potential difference, I is the electric current, and R is the resistance.


5 Resistance

Resistance is the opposition to the flow of electric current. It depends on the length, cross-sectional area, and material of the conductor.


6 Resistivity

Resistivity is the property of a material that opposes the flow of electric current. It is measured in ohm-meters (Ωm).


7 Combination of Resistors

Resistors can be combined in series, parallel, or a combination of both.


8 Cells and Batteries

A cell is a device that converts chemical energy into electrical energy. A battery is a group of cells connected together.


9 Internal Resistance

Internal resistance is the opposition to the flow of electric current within a cell.


10 Potential Difference and Emf

Potential difference is the difference in electric













potential between two points. Emf is the energy per unit charge that a cell supplies to a circuit.


11 Kirchhoff's Laws

Kirchhoff's laws are two fundamental laws that describe the behavior of electric circuits.


12 Wheatstone Bridge

Wheatstone bridge is a device used to measure the resistance of a conductor.






Important Formulae:

1. I = Q/t

2. V = IR

3. R = ρ(l/A)

4. P = VI

5. E = V + Ir


Important Concepts:

1. Electric current and its measurement

2. Ohm's law and its applications

3. Resistance and resistivity

4. Combination of resistors

5. Cells and batteries

6. Internal resistance and emf

7. Potential difference and Kirchhoff's laws


Solved Examples:

1. A wire of resistance 10 Ω is connected to a battery of emf 2 V. Calculate the current flowing through the wire.

2. A cell of emf 1.5 V and internal resistance 0.5 Ω is connected to a resistor of 2 Ω. Calculate the current flowing through the circuit.

3. A Wheatstone bridge is used to measure the resistance of a conductor. If the resistances of the four arms are 10 Ω, 20 Ω, 30 Ω, and R Ω, calculate the value of R.


Practice Questions:

1. Define electric current and state its unit.

2. Derive Ohm's law and explain its significance.

3. Calculate the resistance of a wire of length 10 m and cross-sectional area 0.1 mm^2.

4. A battery of emf 2 V is connected to a resistor of 5 Ω. Calculate the current flowing through the circuit.

5. Explain the concept of internal resistance and its effect on the current flowing through a circuit.


*CBSE Board Important Questions:*

1. Define electric current and explain its unit. (2019)

2. Derive Ohm's law and explain its significance. (2018)

3. Calculate the resistance of a wire of length 10 m and cross-sectional area 0.1 mm^2. (2017)

4. A battery of emf 2 V is connected to a resistor of 5 Ω. Calculate the current flowing through the circuit. (2016)

5. Explain the concept of internal resistance and its effect on the current flowing through a circuit. (2015)


Note: These notes are based on the CBSE board syllabus and are meant to provide a comprehensive overview of the chapter. However, it's always best to refer to the NCERT textbook and other recommended resources for a more detailed understanding of the concepts.

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