Handwritten Notes of Physics Chapter 3: Electric Current
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Bihar Board - Class 12 Physics - Chapter 3: Electric Current Handwritten Notes

BSEB > Class 12 > Handwritten Notes > Chapter 3: Electric Current Handwritten Notes

Electric current is the flow of electric charge through a conductor, driven by a potential difference. It is a fundamental concept in electrical circuits and forms the basis of modern electrical and electronic systems. This chapter discusses the nature of current, its measurement, and the laws governing its behavior in circuits.

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Key Points

  1. Electric Current (II)

    • Definition: The rate of flow of charge through a conductor.
      I=QtI = \frac{Q}{t}
      where QQ is the charge and tt is time.
    • Unit: Ampere (A).
    • Direction: By convention, current flows in the direction of positive charge flow (opposite to electron flow).
  2. Types of Electric Current

    • Direct Current (DC): Charges flow in a single direction (e.g., from batteries).
    • Alternating Current (AC): Charges periodically reverse direction (used in power supply systems).
  3. Ohm’s Law

    • States the relationship between voltage (VV), current (II), and resistance (RR):
      V=IRV = I \cdot R
    • Resistance depends on the material, length, cross-sectional area, and temperature of the conductor.
  4. Resistivity and Conductivity

    • Resistivity (ρ\rho): A material property indicating resistance per unit length and cross-sectional area.
      R=ρLAR = \rho \frac{L}{A}
    • Conductivity (σ\sigma): Reciprocal of resistivity, indicating a material's ability to conduct electricity.
  5. Electrical Power and Energy

    • Power (PP): The rate at which electrical energy is consumed or produced.
      P=VI=I2R=V2RP = V \cdot I = I^2 \cdot R = \frac{V^2}{R}
    • Energy (WW):
      W=Pt=VItW = P \cdot t = V \cdot I \cdot t
    • Unit of energy: Joules (J) or kilowatt-hours (kWh) in practical usage.
  6. Kirchhoff’s Laws

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

    • Used in powering electronic devices, appliances, and industrial machines.
    • Essential in lighting, heating, and communication systems.

Conclusion

Electric current is a cornerstone of electrical engineering, enabling the operation of circuits and devices. By understanding its properties, laws, and applications, we can effectively design and analyze electrical systems for a wide range of practical uses.

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