They are in the distant future, why didn't they use EMP weapons to destroy the Skynet machines? They could've used some sort of similar mass scale weapon to render the Skynet machines useless?
We're not in the world of The Matrix, where EMPs grow on trees. Based on Terminator 3, it looks like we're dealing with, more or less, the same technology we're dealing with now. Based on that, there's two reasons
- The only way to make an EMP right now is with a nuclear weapon. While machines in general are not immune to the destructive effects of radiation, they're not as affected by it as humans are either. So you'd probably make the situation much worse, especially since machines could tolerate more radiation than humans.
Skynet, and its machines, are likely hardened against EMP. You might get a few knocked out, but probably not enough to make a difference and there's no guarantee it would affect all models the same way
The T-800 operates using electronics that are more advanced than what we have now, but they are electronic systems nonetheless. It would be possible to build a faraday-cage like structure around the electronics to protect them, but from what we've seen of the T-800, I doubt that is the case. A powerful enough EMP would kill it.
The T-1000, however, has no electrical circuitry. It is some form of advanced liquid metal that has the ability to manipulate itself and be controlled by an AI. Whatever technology is behind it (perhaps nanobots) is way, way beyond us. There is no indication that it has any system which would be vulnerable to an electromagnetic pulse. My vote is no.