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Connection in seriesConnection in parallelWhen two or more resistors are connected in series, the same current flows through them all, but the total voltage is divided among the resistors. In other words, resistors in series act as a voltage divider.When two or more resistors are connected in parallel, the same voltage is applied across them all,but the total current is divided among the resistors. In other words, resistors in parallel act as a current divider.Figure 1 shows a voltage divider and a current divider built of two resistors each. Figure 1. Resistors in series act as a voltage divider (left panel); resistors in parallel act as a current divider (right panel). Each divider can include more than 2 resistors. The connection in series is part of any power application of electricity, because the conducting wires are always in series with the useful load such as a motor or a lamp. Thus the voltage, for example, 120 V from the power grid, is divided between the wiring and the load. Our goal is to ensure that electric power is delivered to the load but not wasted in the wiring. The connection in parallel is part of any power distribution system: for example, in your household, all appliances and lights are connected in parallel to the same 120 V voltage source – the power grid. The resistances of individual lamps and appliances determine how much power each of them absorbs from the grid. For the analysis of these (and any other) circuits we apply KCL, KVL, and Ohm’s law. Figure 2 shows the calculations for voltage and current division side by side, for the sake of comparison. Book Page 49
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