What is a Jewell?

Question

In a surge protector.

Answer 1

I think you mean joule.

Some surge protector manufacturers tout a device's Joule rating, or the amount of energy that the metal-oxide varistor (MOV) can safely handle. But even though many manufacturers advertise high Joule ratings, implying that this is equivalent to a more powerful surge protector, the joule rating really means little. That's because to raise a Joule rating, all a manufacturer needs to do is put more MOVs inside the MOV surge protector. But, as the old saying goes, the chain is only as strong as its weakest link. When one MOV goes out, the whole chain breaks.