Which one of the following self-made sentences sounds more natural to you in each group:
Group 1
- 1 - We can’t receive radio signals because the transmitter is faulty.
- 2 - We can’t receive radio signals because the transmitter is defective.
- 1 - The car brakes are faulty.
- 2 - The car brakes are defective.
For me, both sentences in both groups work properly.
While both are synonymous, faulty can be freely used where the problems were not due to the manufacturer, while defective may carry the idea that the manufacturer had a hand in causing the problem.
Consider your transmitter examples. A faulty transmitter is simply one that isn't working properly. Something might have broken due to mishandling, or the manufacturer might not have calibrated something properly. Objectively, it could also be called a defective transmitter, but in practice, calling it defective can imply that the problem stems from the time it was put together.
Up until now I have used the two words as follows - faulty as being that it was in order but is now not functioning e.g. a switch used to work but now it doesn't. Defective - that right from the start the product or article is in some form or another incomplete or deficient of something which thus causes it not to work.
All sentences are completely valid as faulty and defective are synonymous.
Personally, in British English, faulty is more common, a mechanic would probably use the word faulty over defective when speaking to you. If it was an official document of some form, defective would most often be used as it is more formal.
Lawrence's answer is very close but not quite precise.
A defect is a flaw that prevents it from performing to design expectations. So if the transmitter contains a component that is designed to last five years and it fails after one year due to a flaw (as opposed to abuse), It's defective.
Faulty just means that it isn't working. If that part mentioned above failed after ten years, it would be faulty because it isn't working, but it wouldn't be defective because it wasn't designed to last that long.
In common usage, though, the terms are applied less precisely, and often used more or less interchangeably.
