Resistances In Series:

Whenever you place resistances in series, their ohmic values add up to obtain the total resistance. This is naturally simple, and it is easy to keep in mind.

PROBLEM:

Assume that the resistances below are hooked up in series with each other: 112 ohms, 470 ohms, and 680 ohms which are as shown in figure below. Compute the total resistance of the series combination?

SOLUTION:

Simply add the values, getting a total of 112 + 470 + 680 = 1,262 ohms. You can round this off to 1,260 ohms. It totally depends on the tolerances of the components-how much their real values are permitted to vary, as an outcome of manufacturing procedures, from the values identified by the vendor. Tolerance is more of an engineering concern than a physics concern; therefore we won't worry about that here.