PC 12V fan and neagtive voltage

[boylesg]

Why won't a PC fan work with GND attached to the red wire and -12V attached to the black wire?

 

[abdulwahababid]

I think loop is not completed via ground in case of DC current.
In Transmission systems the return path is the neutral i (for AC) and the -ve terminal (for DC).we cannot say it as ground technically.

Current will always flow from the higher potential difference to the lower potential difference!

There are two different theories: Both work just as good as the other.

The first theory is the electron flow theory used by Electronics engineers.

The second theory is the conventional current flow theory or as it is also called the hole flow theory is used by electrical engineers.


In the electron flow theory the electrons flow from the negative terminal to the positive terminal.

In the convention current flow theory the current flow from the positive terminal to the negative terminal. But in the conventional theory it is not electrons flowing it is the holes left by the electrons as they drift toward the positive teminal hence the term hole flow theory.

The negative terminal is the terminal with an excess of electrons.
The positive terminal is the terminal with an excess of holes where electrons used to be until they were forced to drift through the power source to the negative terminal.
That is what gives you your potential difference. between the negative terminal and positive terminal.

Actually you shouldn't say negative current flow because current is either flowing or it isn't. It doesn't make any difference which direction down the wire it is going.

In a DC circuit current is always flowing the same direction from negative to positive if you are using the electron flow theory.
If you are working with the hole flow or conventional flow theory the current is flowing from the positive terminal to the negative terminal.