Kirchhoff's two laws as direct consequences of conserving charge and energy, the internal resistance that pulls the terminal P.D. below the e.m.f., and the potential divider that taps off any voltage you need. From a single cell with a load to thermistors and LDRs steering a sensing circuit. Play the three simulations below. The gamified lessons, the topic Paper 1 practice, and the concept map are all live below too.