CBSE Class 12 Physics Notes, Free PDF download of CBSE Class 12 Physics revision notes and short key-notes to score more marks in your exams, prepared by our expert Physics teachers from the latest edition of CBSE (NCERT) books.

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Current Electricity Class 12 Classnotes with Numericals and PDF | Download Physics Notes

 Chapter Notes: Current Electricity (Class 12 Physics)

Current Electricity Class 12 Classnotes with Numericals and PDF | Download Physics Notes
Current Electricity Class 12 Classnotes with Numericals and PDF | Download Physics Notes



Current Electricity Class 12 Classnotes with Numericals and PDF | Download Physics Notes

1. Introduction to Current Electricity:

   Current (I): The flow of electric charge in a conductor is termed as current. It is measured in Amperes (A).

   Conventional Current vs Electron Flow: Conventional current assumes that positive charges flow, while in reality, electrons (negatively charged) move. However, for simplicity, conventional current is considered in circuit analysis.


2. Electric Current and Drift Velocity:

   Drift Velocity `(v_d)`: It is the average velocity of charged particles (electrons in a conductor) in response to an electric field.

Relation between Current and Drift Velocity: `(I = nAe v_d)`, where I is the current, n is the charge carrier density, A is the cross-sectional area, e is the charge of an electron.


3. Ohm's Law:

   Ohm's Law Equation:(V = IR), where V is voltage, I is current, and R is resistance.

   Ohmic and Non-Ohmic Conductors: Materials following Ohm's law are ohmic conductors; others are non-ohmic.


4. Electrical Resistance:

   Resistance (R): Opposition to the flow of electric current. Measured in Ohms `\(\Omega\)`.

   Factors Affecting Resistance: Length (l), Cross-sectional Area (A), Temperature (T), and Material.


5. Resistivity (ρ) and Temperature Dependence:

   Resistivity (ρ): Intrinsic property of a material to oppose the flow of current.

   Temperature Dependence: Resistivity increases with temperature for most conductors.


6. Combination of Resistors:

   Series Combination:` \(R_{\text{total}} = R_1 + R_2 + R_3 + \ldots\)`

   Parallel Combination:` \(\frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \ldots\)`


7. EMF and Internal Resistance:

   Electromotive Force (EMF): Voltage supplied by a source like a battery.

   Internal Resistance (r): Resistance within the source.

   Terminal Voltage: `\(V = \text{EMF} - Ir\)`


8. Kirchhoff’s Laws:

   Kirchhoff’s Current Law (KCL): At any junction in a circuit, the total current entering equals the total current leaving.

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


9. Electric Power and Heating Effect:

   Power (P): Rate of doing work. `\(P = VI = I^2R = \frac{V^2}{R}\)`

   Heating Effect: Electric power can produce heat in resistors. `\(H = VIt = I^2Rt = \frac{V^2t}{R}\)`


10. Numerical Problems:

   1. Calculate the current flowing through a resistor of 10 ohms when a voltage of 5 volts is applied.

   2. Determine the resistance of a wire with a length of 2 meters and a cross-sectional area of 0.5 cm², given the resistivity as `\(2 \times 10^{-7} \, \Omega \cdot \text{m}\).`

   3. Find the total resistance of resistors in series: `\(R_1 = 3 \, \Omega\), \(R_2 = 5 \, \Omega\), and \(R_3 = 2 \, \Omega\).`

   4. Calculate the power dissipated in a resistor of 8 ohms when a current of 4 amperes flows through it.


These chapter notes provide a comprehensive overview of the key concepts in Current Electricity, including definitions, equations, and numerical problems for practice.

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