# What is this component marked 10mΩJ?

Can someone help me to identify this component marked "10mΩJ?" I'm pretty sure it's a 10 mega ohm resistor, but I can't find it anywhere to buy one. Maybe a similar resistor can work, but I don't have more information, like type and how much it can handle since it is for a ballast (car light control circuit.)

• It's milli, not Mega. Probably a current shunt. Any ballpark guess at specifications require more context. Aug 21, 2022 at 21:45
• Related: "What is ohm joules ( ΩJ ) unit used for?" and "What is the meaning of "ΩK" on a wirewound resistor?". Those explain the markings on the component here, but they don't answer the request for details of the rating of the specific component in this question, so they aren't quite a duplicate. Aug 22, 2022 at 1:03

It is a 0.01$$\\Omega\$$ (10m$$\\Omega\$$) resistor with tolerance +/-5% (J).

Chances are pretty good that if it's burned up then something else (such as a semiconductor) is kaput as well.

• Doubling down on that "something else is kaput" comment. Resistors don't burn up by themselves. So when you go to fix it, you want to look at what else is damaged (and accept that there may have been a chain reaction, and your best bet may be to just get a new controller). Aug 21, 2022 at 22:22

'm' for milli, 'M' for mega.

If it's for a lighting circuit it might be a current shunt and so 10 mΩ (0.01 Ω) would make sense. The controller will monitor the voltage drop across the shunt and use that to determine whether the light is off, on or short-circuited. From Ohm's law you can calculate the voltage drop per ampere of current through the lamps, $$\ V = IR = I \times 0.01 \$$ so 1 A would give a signal of 10 mV.

'J' may be a tolerance. In the SI system of units it is the symbol for 'joule', the unit of energy. This is unlikely to be its purpose on this marking.

• Aug 21, 2022 at 21:53
• Although to be fair, you sometimes would see "M" or "MF" for "micro(farad)" on really old capacitors &c. Aug 22, 2022 at 17:36