Direct-Current Circuits (Physics)

Recall cards on direct-current circuits. Electromotive force: emf as work per unit charge, the symbol epsilon, the volt, energy conversion, terminal voltage, internal resistance r, V_terminal = emf - I r, I = emf/(R + r), and ideal versus real batteries. Resistors in series and parallel: the same current in series, R_S as a sum, the source voltage as a sum of drops, the same voltage in parallel, 1/R_P as a sum of reciprocals, branch currents summing to the total, and combination circuits. Kirchhoff's rules: junctions, the junction rule from charge conservation, the loop rule from energy conservation, and the sign conventions for resistors and emf sources. Electrical measuring instruments: the ammeter in series, the voltmeter in parallel, the galvanometer, converting it to an ammeter or voltmeter, and analog, digital, and ohmmeter designs. RC circuits: charging and discharging of a capacitor, the time constant tau = RC, the 63.2% and 36.8% marks, and a full capacitor as an open circuit. Household wiring and safety: thermal and shock hazards, short circuits, P = I^2 R_w, fuses and breakers, the live, neutral, and ground wires, grounding, and the GFCI.