I recently bought a Raspberry Pi 3. But unfortunately the first one I got was damaged. We managed to get it going but one USB port was rendered useless. Now I want to know whether it would cut down power consumption by disabling the use of the USB(if so how?) or does it do the same thing just tearing the port off? By the way I am running Raspbian.
The USB ports run off a single USB controller so you can't just disable a single one. And the ethernet also runs off the controller, so you wouldn't be able to use it if you disabled it. Even if you did disable USB, it would save very little power. Wifi, CPU and RAM use the most energy, as well as the graphics processor. To use less power you could also disable the LEDs which would probably help more than turning off the USB controller.
So reduce the software running on your Pi that uses a lot if CPU, that will help the most. And use ethernet instead of wifi if you can. Disable graphical output if you're working headless.
"Tearing" off the USB ports is a really bad idea, and wouldn't do anything anyway.