Kirchhoff’s Laws Kirchhoff’s Current Law Kirchhoff’s Voltage Law Series Circuits Parallel Circuits Polarity

Kirchhoff’s Current Law Key Point: The number of charges per second (current) flowing to a point in a conductor must equal the number of charges flowing from that point. (See Figure 10 ‑ 35.)

Kirchhoff’s Voltage Law Key Point: Around any closed path, the sum of potential rises must equal the sum of potential drops. Σ E = Σ V. E=V 1 +V 2

Series Circuits Key Point: In a series circuit: (1) the current is the same throughout the circuit; (2) the sum of the voltage drops must equal the emf I T = I 1 = I 2 = I N E = V 1 +V 2 +…+V N

Parallel Circuits Key Point: In a parallel circuit: (1) the voltage drop is the same across each branch; (2) the total current into and out of the branches equals the sum of the individual branch currents. V 1 = V 2 = V N I T = I 1 +I 2 +…+I N

Polarity Key Point: In an electrical circuit the polarity of the voltage drops across the individual resistances depends on the direction of current through them. (See Figure 10 ‑ 36.)