Strange resistors

Pieter-Tjerk de Boer, PA3FWM

(This is an adapted version of part of an article I wrote for the Dutch amateur radio magazine Electron, March 2020.)

SMD resistors in bags This picture was taken at a recent amateur radio fleamarket. On offer is a little bag containing 0 ohm SMD resistors. Resistors of 0 ohm aren't strange: they are effectively jumper wires that can easily be mounted by assembly machines.

What is strange though, is that these resistors are specified as having a tolerance of 5 %. Tolerance indicates how much the real resistance can deviate from the nominal value. But 5 % of 0 ohm is still 0 ohm, so it says that the resistor is exactly 0 ohm. That is impossible, because superconductive materials at room temperature have not yet been found, as far as a I know.

It is also strange that the allowed power is specified as 1 watt: after all, if the resistance is really 0 ohm, no power can be dissipated since P = I2R.

(Of course, the above is tongue-in-cheek; 5 % and 1 watt make perfect sense for normal non-0-ohm resistors, and apparently this seller copied that information also on his/her 0 ohm resistors without thinking about it further.)

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