UP Board - Class 12 physics - Chapter 3: Current Electricity Handwritten Notes

Current electricity deals with the flow of electric charges through a conductor in a continuous and controlled manner. The electric current explain the rate of flow of charge through a cross-sectional area of a conductor, and it forms the basis of various electrical systems and applications.

Key Points:

1. Electric Current:

   • It is the flow of electric charge in a specific direction through a conductor.
   • Measured in amperes (A), where 1 ampere = 1 coulomb/second.

2. Types of Electric Current:

   • Direct Current (DC): Charges flow in one direction, e.g., in batteries.
   • Alternating Current (AC): Charges change direction periodically, e.g., in household circuits.

3. Ohm’s Law:

   • The current passing through a conductor is directly proportional to the voltage applied across it and inversely proportional to its resistance.
   • Resistance determines how much a conductor opposes the flow of current and is measured in ohms (Ω).

4. Resistance and Resistivity:

   • Resistance (R): Depends on the material, length, and cross-sectional area of the conductor.
   • Resistivity (ρ): A material property indicating how strongly it resists current flow.

5. Electric Power and Energy:

   • Electric power is the rate at which electrical energy is consumed or produced.
   • Measured in watts (W), it determines the efficiency of electrical appliances.

6. Combination of Resistors:

   • Resistors can be arranged in series (current remains the same, total resistance adds up) or parallel (voltage remains the same, total resistance decreases).

7. Kirchhoff’s Laws:

   • Kirchhoff’s Current Law (KCL): The total current entering a junction equals the total current leaving it.
   • Kirchhoff’s Voltage Law (KVL): The sum of potential differences in a closed loop is zero.

8. Applications of Current Electricity:

   • Power distribution systems, electric circuits, home appliances, and electronics are based on the principles of current electricity.
   • Used in devices like fans, lights, electric vehicles, and more.

Conclusion:

Current electricity forms the backbone of modern electrical engineering and technology. Understanding the flow of charges, the role of resistance, and the behavior of circuits is essential for designing and operating electrical systems. Mastery of these concepts enables innovations in energy-efficient devices and sustainable technologies.

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