✔ How To Size A Resistor Wattage

How To Size A Resistor Wattage

- May 07, 2018

With carbon composition obsolete and carbon film resistors the physical size of the resistor is proportional to its wattage rating. As the dissipated resistor power rating is linked to their physical size a 14 0250w resistor is physically smaller than a 1w resistor and resistors that are of the same ohmic value are also available in different power or wattage ratings.

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So it would be advisable to add a lot of margin.

How to size a resistor wattage. Place the resistor on the outline to make sure they match. You can determine a resistors wattage with a size chart. All you need to worry about is the resistance value and how much power it can take.

Plug in value into ohms law formula. This code contains the width and height of the package. Find the resistor outline on the chart that most closely matches that of the resistor itself.

A 1 watt resistor will be larger than a 14 watt resistor. Pi x e p120 x 12 p144 watts resistor will be dissipating 144 watts at 12v with 120 milli amps flowing thru it. So in the example of 0603 imperial code this indicates a length of 0060 and a width of 0030.

So having a resistor with at least double the wattage required would be advisable. If your schematic does not tell you the necessary power rating for the resistor and you dont know or dont want to know how to calculate it then try using a. With wirewound and other power resistors the wattage rating is usually stamped on the resistor body.

And also temperature will degrade the capacity of the resistor to handle powerfor example a thin film resistor will handle 80 of power dissipation at 85 degrees celsius and 50 at 100 degrees celsius. For most standard circuits you dont need to worry about the types of resistors you choose. Place the size chart see reference on a flat surface.

The size of smd resistors is indicated by a numerical code such as 0603.