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I am learning about resistors and may not understand something fundamental, but are there any reasons to prefer a low wattage resistor over a high wattage one? Other than space & cost, are there any basic problems using a resistor with a power rating much higher than necessary?

user3424554
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  • Duplicate of https://electronics.stackexchange.com/questions/149198/other-than-cost-is-there-a-reason-to-not-use-higher-rated-components-than-calle – user3424554 Sep 26 '21 at 11:28
  • Yes, thank you :) – user3424554 Sep 26 '21 at 11:33
  • Measure a 3 kW kettle element with a DMM. It will measure in the ballpark of 20 ohms. It will be dissipating mW or even uW due to the DMM's measuring current. – Neil_UK Sep 26 '21 at 14:24

2 Answers2

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You are not missing anything, except maybe undervalue the importance of size and cost.

If a circuit needs a 1/8W resistor and you use a 1/4W or even a 1/2W, there isn't really much of a difference (mostly). However, a 1000W resistor is outright massive, can be over 30cm in length and 4 cm in diameter, whereas a 1W resistor can be tiny, some come in a 0402 surface mount package.

So in general, you can use higher power resistors but space and cost are very dominant factors when you design real circuits.

Yiannis
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You may find that higher power resistors are not available with value tolerances as tight as lower power ones. There may also be fewer resistance values, and available values may tend to be lower. Also higher power resistors may have higher inductance. Temperature coefficient of resistance is another possible problem area although you wouldn't need to worry about resistance change due to self heating.