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Step 1
Examine the effect of a resistor on a circuit. The voltage drop caused by a resistor may be calculated by Ohm's law: that V=IR where V is the drop in voltage, I is the current in the circuit and R is the resistance of the resistor.
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Step 2
Place a resistor in the circuit on each side of an electrical component to control the voltage that reaches the component. This is a reliable way of protecting a component from excess voltage.
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Step 3
Identify the resistance of a resistor by the color-coding scheme. The four-band color scheme is the most common for components used by students and electronics hobbyists. However, the Surface Mount Technology (SMT) coding scheme is more common in modern electronics.
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Step 4
Study the four-band identification system. The four bands of color are painted all the way around the resistor to provide the resistance in Ohms. The first two bands give the first significant digits the resistance, the third provides the multiplier for the base value and the fourth band (if present) gives the tolerance of that value.
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Step 5
Use the industrial type designation for a resistor. This scheme also provides the resistance value and tolerance of that value as well as the power rating. The power rating of a resistor is the amount of heat (in watts) that the resistor can tolerate.
