Kirchoff’s Voltage Law

12PHYS - Electricity

Finn Le Sueur

2024

Mahi Tuatahi

Calculate the voltage used by each resistor.
Strategy: Start by calculating the total resistance and the total current.

Kirchoff’s Laws: Voltage

The sum of the potential differences (voltages) in any closed loop is zero.
OR: That is to say, over a loop, the full voltage (energy) of the power supply must be consumed.

\[ \begin{aligned} V_{1} + V_{2} + V_{3} &= 0 \newline V_{1} + V_{4} &= 0 \end{aligned} \]

Series Circuit Parallel Circuit
Current (I) in Amperes, \(A\) Same through all components Adds up to the supply
Voltage (V), in Volts, \(V\) Adds up to the supply Same across all equi-resistant paths
Resistance (R) in Ohms, \(\Omega\) Combine to give more resistance (\(R_{T}=R_{1}+R_{2}+...\)) Combine to give less resistance (\(\frac{1}{R_{T}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+...\))

Pātai: Harder

Calculate all unknown values.
Strategy: You should start by calculating the total resistance and total current. Then, calculate the voltage used by the resistor in series with the power supply.

Practice

  • Textbook Activity 18B Q1, 3
  • Homework Booklet: B1
  • Fast Finishers: B3

Homework: A5, B2 due Monday!

Confirming Kirchoff’s Voltage Law

  • Collect a Kirchoff’s Voltage Law sheet from the front.
  • In a small group set up a station with a hardmat to protect the bench.
  • Follow the instructions to set up each circuit in turn, take the required measurements and answer Task 1-4.