Lesson 10.5: DC Circuits & Kirchhoff’s Laws - Summary

Key Concepts: DC Circuits & Kirchhoff’s Laws

Series Circuits

  • Same current through all components: I_total = I₁ = I₂.
  • Voltages add: V_total = V₁ + V₂.
  • Resistances add: R_total = R₁ + R₂.

Parallel Circuits

  • Same voltage across all branches: V_total = V₁ = V₂.
  • Currents add: I_total = I₁ + I₂.
  • 1/R_total = 1/R₁ + 1/R₂.

Kirchhoff's Laws

  • Junction Rule (KCL): Total current into a junction = total current out. (Conservation of charge.)
  • Loop Rule (KVL): The sum of all voltage gains and drops around any closed loop = 0. (Conservation of energy.)

Problem-Solving

  • Assign current directions (guess if needed — a negative answer means opposite direction).
  • Write KCL for junctions and KVL for loops. Solve the system of equations.
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