If the external monitor works fine then most likely there is nothing wrong with the motherboard or video card and the problem is somewhere inside the laptop display panel.
Here's what I usually do in order to narrow down problems like this:
1. I reseat the video cable connectors on both ends, on the motherboard/video card and on the back of the LCD screen. If the video cable gets loose, it might cause a problem like on your laptop.
2. Replace the video cable
3. Replace the LCD screen
nothing can affect a computer
unless it blew out when it was connected to that monitor nothing should happen unless it send like wrong amounts of electricity which i highly doubt possible.
Monitor is not plugged in or monitor is not plugged in to computer
Assuming there is power to the monitor (the 'on' indicator is illuminated)... Check the cable from the monitor to the CPU is connected... (try another cable to be sure). If that's okay - the next thing to check would be the graphics card inside the computer (best done by a competent technician).
No. What purpose does a mouse serve with nothing to process its clicks? What good does a monitor do with no computer to send it information? Input and output devices are peripheral devices and need to be connected to the processor to serve a purpose.
nothing.
If nothing happens when you press the power button, make sure all the wires are connected. make sure that both the computer and the monitor are plugged into a power source. Also, make sure that the monitor is connected to the computer. If it still does not turn on, you might be having a problem with one of the components in your computer. At this point I would take it to a specialist and have them figure out what the problem might be.
The current depends on what is connected to the battery's terminals. If nothing is connected to it, then there is no current, and the battery lasts quite a while. In general, the current is 1.5/resistance of the external circuit connected to the battery until that number gets too big, and then the voltage of the battery sags, because it can't deliver that much current.
Central Processing Units do not have "external units". There are many things outside (external to) the CPU, but nothing named an "external unit".
nothing
No, when nothing is connected, no power is used even though the circuit is live and ready.
nothing