Junction box for what? Do you mean a sub panel?
You don't; you call an electrician out to safely finish the job for you.
The answer depends on what type of access you have to the junction box. The wire external to the box may have some slack that can be brought into the box. If everything is tight you will probably have to install one or more additional junction boxes or rerun wire from electric panel. As an example assume that the short wire has no external slack, but you can install a new junction box near the other box and in the path of the short wire. 1. Pull the short wire from existing junction box. 2. Install new box in path of short wire so more slack will be available in the additional junction box; and pull wire into new box. 3. Run a wire of the same size from new to old box and re-splice any connections for original short wire or new connections; and connect this new wire to the original short wire in the new box. Make sure you follow all code requirements for your locale.
Yes. Just make sure you keep the junction box accessable to meet code. Also if you are extending the outlet to more than 75 feet away from the panel you should run 4-3 wire.
Connect the green wire to the bare wire in the junction box. Connect the white wire to the white wire in the junction box. Connect the black blue wires to the black wire in the junction box. The black is usually the fan and the blue is usually the light on the fan. They seperate them in case you wish to hook the fan/light to two switches.
No it is not a standard practice. That said you will find such a connection from a light fixture junction box, that has the supply source in it, down to a a light switch junction box. The neutral for the light is already at the light junction box but the switched leg has to go down to the switch. The black "hot" wire is connected to the white wire in the cable going to the switch and from the switch it returns in the black wire in the same cable which is then connected to the light fixture.
If you do not add a junction box it looks like new wire all the way from the old junction box with new wire that is longer. It's a tough place to be.
A 240 volt wire is the insulation factor of the wire. If you mean a 240 supply source from a distribution panel to a junction box then the answer is yes. You have to keep in mind that the box has to be accessible, meaning that you can get to the box to check the splice within the box. Don't bury the junction box behind the wall board.
You don't; you call an electrician out to safely finish the job for you.
The answer depends on what type of access you have to the junction box. The wire external to the box may have some slack that can be brought into the box. If everything is tight you will probably have to install one or more additional junction boxes or rerun wire from electric panel. As an example assume that the short wire has no external slack, but you can install a new junction box near the other box and in the path of the short wire. 1. Pull the short wire from existing junction box. 2. Install new box in path of short wire so more slack will be available in the additional junction box; and pull wire into new box. 3. Run a wire of the same size from new to old box and re-splice any connections for original short wire or new connections; and connect this new wire to the original short wire in the new box. Make sure you follow all code requirements for your locale.
Yes. Just make sure you keep the junction box accessable to meet code. Also if you are extending the outlet to more than 75 feet away from the panel you should run 4-3 wire.
No, do not mix aluminum wire with copper wire.
Connect the green wire to the bare wire in the junction box. Connect the white wire to the white wire in the junction box. Connect the black blue wires to the black wire in the junction box. The black is usually the fan and the blue is usually the light on the fan. They seperate them in case you wish to hook the fan/light to two switches.
The wire nuts do not have to be inside the junction box. They must, however, be as tight as possible to keep moisture from inside the light fixture.
Using a box that is hire voltage than what you need can cause a short, and even a fire. So using a 240V box, when all you need is a 110v receptacle, wouldn't be a good idea.
There is no restriction on different size wires being spliced in the same junction box. If your question involves splicing 8ga. to 10ga, this also is not a problem so long as the circuit allows for 10ga wire.
The pre wire for a ceiling fan light should be made with a three wire cable. This cable will have a red, black, and white wire as main conductors. This cable will also have a bare ground wire. This wire should be strung between a two gang switch box to the fixture junction box. This pre wire allows the supply to be either fed to the two gang box. From the two gang switch junction box, one side will be used for the light in the fixture and the other side of the switch junction box, itwill be used for the fan portionin the fixture.
No it is not a standard practice. That said you will find such a connection from a light fixture junction box, that has the supply source in it, down to a a light switch junction box. The neutral for the light is already at the light junction box but the switched leg has to go down to the switch. The black "hot" wire is connected to the white wire in the cable going to the switch and from the switch it returns in the black wire in the same cable which is then connected to the light fixture.