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I have seen many zero ohm resistors which says that maximum resistance is say 50 mOhm. But, the maximum current rating will be only 1 amps. 0603 package. Power rating they mention as 1/8 watt. Can anybody comment on this differing I^2 * R and power rating?

Edit: My purpose of question is to clarify doubt in a datasheet which has both current rating and power dissipation. Which one should i consider?

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  • \$\begingroup\$ Your edited question is answered by stevenvh in the question I linked to. You must consider both. The maximum current rating together with the resistance gives a certain amount of power disipation. If the power rating is higher than the calculated disipation at the rated current then use the power rating else use the current rating. \$\endgroup\$ – JRE May 29 '15 at 14:26
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If a transistor had a max voltage rating of 100 volts and a max current rating of 10 amps, it doesn't mean it has a max power rating of 1000 watts - the max ratings supplied in the data sheet are extremes and not to be used in partnership with other extremes to forge some hyper-extreme max value.

If the max current is 1A (DC or RMS) then make sure you don't go above it and if the power rating is 125 mW then it cannot be exceeded but in reality that package power dissipation is for resistors of the same style/package having a finite specified resistance.

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  • \$\begingroup\$ Isn't I only comparing one parameter? Is there any other way to check the power dissipation across the resistor? \$\endgroup\$ – User323693 May 29 '15 at 14:17
  • \$\begingroup\$ Which one shall I consider? \$\endgroup\$ – User323693 May 29 '15 at 14:17
  • \$\begingroup\$ Shall I go with the 1A rating parameter, as it is minimal? \$\endgroup\$ – User323693 May 29 '15 at 14:19
  • \$\begingroup\$ @KumarGR you have no choice but to go with the 1 amp rating. If a resistor in the same range were 0.15 ohm then you'd exceed the power rating for 1A continuous but you could still have 1 amp as a peak limit for short durations - for the length of a short duration this might be 10 ms or 1 second but the data sheet would tell you. On the other hand if the data sheet said the max limit were 1A RMS then for a sinewave the peak current could be as high as 1.4142 amps. It's all down to what the data sheet says and, if unclear, then post the section in your question OR contact the supplier. \$\endgroup\$ – Andy aka May 29 '15 at 14:37
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Very likely if you exceed the spec power rating, the heating causes a rise in temperature which leads to a rise in resistance and thus higher power dissipation. So much more like the filament of a light bulb rather than a 'linear' resistor.

The resistance is linear over a limited and specified range but when you push things, self-heating happens and matters go nonlinear. Heed the specs.

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Both should be observed. P = IV, where P should be less than .125 Watts, and I should be less than 1 Amp, in any circumstances.

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