Core Unit III: Electricity
C. Electric Circuits

1. Kirchhoff's Laws

Key Concepts

Kirchhoff's Laws are applications of two fundamental conservation laws: the Law of Conservation of Energy, and the Law of Conservation of Charge.

At any junction in an electric circuit, the total current flowing into the junction is the same as the total current leaving the junction. (Kirchhoff's Current Law, or Kirchhoff's First Law)

The algebraic sum of the potential differences in a complete circuit must be zero. (Kirchhoff's Voltage Law, or Kirchhoff's Second Law)

Kirchhoff's Laws are useful in understanding the transfer of energy through an electric circuit. They are also valuable in analyzing electric circuits.

Learning Outcomes

Students will increase their abilities to:

1. Recognize that Kirchhoff's Laws are applications of the Law of Conservation of Energy, and the Law of Conservation of Charge.

2. State Kirchhoff's First Law (Kirchhoff's Current Law).

3. State Kirchhoff's Second Law (Kirchhoff's Voltage Law).

4. Use Kirchhoff's Laws to assist in understanding the transfer of energy through electric circuits.

5. Use Kirchhoff's Laws to solve problems related to electrical circuit analysis.

Teaching Suggestions, Activities and Demonstrations

1. Use a D.C. network. Investigate relationships between resistance, potential difference, and current. The network should consist of at least two loads in parallel connected to at least one other load in series. Record measurements of current and electric potential in different parts of the circuit. Adjust the potential of the source and repeat.

   Using the results, search for relationships between current, electric potential, and resistance in different parts of the network.