Electronics All-in-One For Dummies. Doug Lowe

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       When you measure the resistance of an individual resistor or of circuits consisting of nothing other than resistors, it doesn’t matter what direction the current flows through the resistor. Thus, you can reverse the multimeter leads and you’ll still get the same result.

       Some components such as diodes pass current better in one direction than in the other. In that case, the direction of the current does matter. You can learn more about this effect in Book 2, Chapter 5.

       Resistors aren’t perfect. Thus, a 470 Ω resistor rarely provides exactly 470 Ω of resistance. The usual tolerance for resistors is 5 percent, which means that a 470 Ω resistor should have somewhere between 446.5 Ω and 495.5 Ω of resistance. For most circuits, this amount of imprecision doesn’t matter. But in circuits where it does, you can use the ohmmeter function of your multimeter to determine the exact value of a particular resistor. Then, you can adjust the rest of your circuit accordingly. (More on this in Book 3, Chapter 2.)