How to Determine Resistor Wattage Based on Size

A resistor is a standard electronic component that has a constant electrical resistance in a circuit. In addition to a resistance value, measured in ohms, it has a maximum power rating, measured in watts. When a circuit does not exceed the power rating, the resistor works reliably and without fuss for decades. Exceed the power rating by more than a few percent, and the resistor burns up within minutes. Generally, the larger the resistor, the more power it handles. You can determine a resistor's wattage with a size chart.

Things You'll Need

• Resistor size chart

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Instructions

1. • 1

     Place the size chart (see reference) on a flat surface.

   • 2

     Find the resistor outline on the chart that most closely matches that of the resistor itself.

   • 3

     Place the resistor on the outline to make sure they match.

   • 4

     Read the wattage value on the chart next to the outline.