Chapter 26: Direct-Current Circuits

Kirchhoff's junction rule, based on charge conservation, states that the algebraic sum of currents entering any circuit node equals zero, while the loop rule, derived from energy conservation, requires that voltage changes around any closed path sum to zero. These principles generate systems of linear equations that enable complete circuit analysis for complex networks with multiple sources and branches. The chapter extensively covers electrical measurement instruments, explaining how ammeters with minimal internal resistance connect in series to measure current, while voltmeters with high internal resistance connect in parallel to measure potential differences, with both instruments utilizing shunt and series resistors respectively to extend their measurement ranges. Resistor-capacitor circuits receive detailed treatment, examining exponential charging and discharging processes characterized by the time constant tau equals RC, where capacitors reach approximately sixty-three percent charge after one time constant during charging and retain thirty-seven percent during discharging. The material concludes with practical power distribution systems, contrasting household alternating current wiring with automotive direct current systems, emphasizing safety devices including fuses, circuit breakers, and ground-fault circuit interrupters that protect against dangerous current conditions and electrical hazards.