You can’t classify red as either positive or negative without taking the situation or setting into account. Consider the following:
1). Jumper Cable – Red Wire Is Positive
In jumper cables, red wire is the positive line. It connects to the positive terminal on a battery. The black wire is the negative wire, and it runs to the negative terminal.
2). Speakers – Red Wire Is Positive
Polarity matters to speakers. Contrary to what people think, reversing the polarity won’t damage the speakers. They will refuse to work, or the sound quality will deteriorate drastically, which is more of an annoyance than anything.
You can avoid such inconvenient situations if you remember that red is positive and black is negative. You also have white (or yellow), which is positive, and blue, which is negative. You are less likely to miswire speakers because they have manuals that show you where each wire goes.
These manuals will also tell you the polarity of each color. You can only go wrong if you ignore the manual.
3). DC Circuits – Red Is Positive
The polarity matters to DC circuits because the electrons flow in one direction. As such, you have positive and negative ends. This is not true for AC circuits. The electrons in an AC circuit can change direction.
Therefore, you don’t see terminals that are consistently positive or negative. In DC circuits, red is positive, while black is negative. White (or grey) points to the ground. The DC power circuit color codes in the US have specifically identified red as the positive (of a negative grounded) circuit.
You also have white, which is the positive (of a positive grounded) circuit. Additionally, red is positive in the 3-wire grounded DC system.
The IEC color scheme differs from what you see in the US. They assign brown to the positive (of a negative earthed) circuit and blue to the positive (of a positive earthed) circuit.
Don’t ignore the location. Each country has a color scheme it follows. That color scheme may change depending on where you live.
4). AC – Red Wire Is Line, Single, 3-Phase
The European AC power circuit color scheme doesn’t mention positive or negative terminals. They use green-yellow, blue, and brown or black to denote ‘Protective Earth,’ ‘Neutral,’ ‘Line, Single Phase,’ and ‘Line, 3-Phase.’
The UK is in a similar boat. Their AC power circuit color scheme doesn’t mention polarities. But in this case, they include a red wire (Line, Single Phase and Line, 3-Phase).
In the US and Canadian AC power circuit color schemes, red is ‘Line, 3-Phase.’ What does this mean? Many experts call the red wire in an AC circuit the positive line
They call the hot wire (the line that carries electricity to an appliance) the positive conductor. Admittedly, they assigned that classification to the black wire because it usually carries the current in a conventional circuit.
It takes power to the outlet. The neutral wire takes that power back to the panel. This is the negative wire. The red wire is similar to its black counterpart because they are both hot. They bring electricity from the panel to the load.
5). Outlet – Red Wire Is Positive
Homeowners in American homes rarely see red wires in outlets. The last time you opened a receptacle, you probably saw a black, white, and green wire. This is because most American homes use 120V.
Angi associates red wires with a 240V outlet. Like the black wire, the red line brings power to the outlet, which is why contractors call it the positive conductor. You may see this color in smoke detection systems where it connects two smoke detectors or in 3-way switches where it moves the current from the first switch to the second. Either way, your contractor is more likely to call it the positive wire.
However, you can’t expect every color scheme to use red as the live wire. For instance, you can identify brown as the live wire in UK plugs. This would make brown the positive line and blue the neutral, while yellow and green are the ground.
You may see both black and red wires in an AC circuit. In such scenarios, wikiHow calls the live black wire the primary positive wire. The red line is also live and positive. Blue is a phase 3 hot wire, while white is neutral.
6). Ceiling Lights – Red Is The Positive Wire
Red is the positive wire in a ceiling light socket. Lines with black and blue sheaths are also positive. White is negative.
If you still have doubts, test the wires with a multimeter. Connect the probes and check the readings. A positive wire will produce a positive number on the screen. A negative wire will produce a negative number.
What Color Wire Does Red Go To?
You can connect a red wire to a black wire (from the circuit) and the white or red wire (from a light fixture) while installing a light fixture. You can also connect black and red wires in smoke detectors.
However, connecting wires with different colors can create sparks, possibly even starting a fire.
This is why the instructions are so important. What are you trying to install? Does it have a manual? If you can mix the colors safely without causing harm, the manual will tell you. If mixing colors is a bad idea, the manual will warn you.
What Happens If Red Wire Is Connected To Wrong Wire?
For instance, connecting the red wire to a neutral wire will cause a short circuit. If you’re lucky, the breaker will trip, depriving your home of power. If the breaker malfunctions, you may start a fire.
This is why contractors are encouraged to label the wires. Labels discourage people from mixing the wrong wires.