Electricity

• Electric Charge ($Q$)
  • Types: Positive and Negative
  • Unit: Coulomb (C)
  • Quantization: $Q = ne$
• Electric Current ($I$)
  • Definition: Rate of flow of charge ($I = Q/t$)
  • Unit: Ampere (A)
  • Measuring Instrument: Ammeter (Connected in series)
  • Direction: Opposite to flow of electrons
• Electric Potential & Potential Difference ($V$)
  • Definition: Work done per unit charge in moving between two points ($V = W/Q$)
  • Unit: Volt (V)
  • Measuring Instrument: Voltmeter (Connected in parallel)
• Ohm's Law
  • Statement: $V \propto I$ at constant temperature
  • Formula: $V = IR$
  • Resistance ($R$)
    • Definition: Opposition to current flow
    • Unit: Ohm ($\Omega$)
    • Factors Affecting Resistance:
      • Length ($l$): $R \propto l$
      • Area of Cross-section ($A$): $R \propto 1/A$
      • Nature of Material (Resistivity, $\rho$)
      • Temperature
• Combination of Resistors
  • Series Combination
    • Formula: $R_s = R_1 + R_2 + R_3$
    • Current ($I$) remains same
    • Voltage ($V$) divides
  • Parallel Combination
    • Formula: $1/R_p = 1/R_1 + 1/R_2 + 1/R_3$
    • Voltage ($V$) remains same
    • Current ($I$) divides
• Heating Effect of Electric Current
  • Joule's Law of Heating: $H = I^2Rt$
  • Applications: Electric Iron, Electric Heater, Fuse wire
• Electric Power ($P$)
  • Definition: Rate of consumption of electrical energy
  • Formulas: $P = VI = I^2R = V^2/R$
  • Unit: Watt (W)
  • Commercial Unit: Kilowatt-hour (kWh) or Board of Trade Unit (B.O.T.)
    • $1 \text{ kWh} = 3.6 \times 10^6 \text{ Joules}$