This document discusses the applications of Thevenin's and Norton's theorems. Thevenin's theorem states that any linear electrical network can be reduced to an equivalent circuit with a voltage source in series with a resistor. This is useful when a load resistor in a complex circuit needs to be changed. Norton's theorem states that any linear network can be represented by a current source in parallel with a resistor. Both theorems allow simplifying complex circuits for analysis. Thevenin's theorem is applied to power systems and circuits where the load resistance varies. Norton's theorem allows focusing on part of a circuit by reducing the rest to a simple equivalent.