In this lesson, the focus is on understanding electric circuits involving resistors, specifically how to calculate current and voltage. Students are introduced to a circuit diagram with a 12-volt battery and two resistors in series and parallel configurations. The teacher explains how to determine if a fuse will blow based on the current flowing through the circuit and guides students through the calculations needed to find total resistance and current, using relevant formulas. The lesson emphasizes hands-on work and checking calculations to understand the behavior of electricity in circuits.