A simple question that’s surprisingly complex. Why? Because there are two answers, not just one.
If we’re talking about typical 110-120 volt AC wiring as commonly found in homes, shops, offices and so on, the black wire is “hot” and white wire is “neutral”. There is also a third wire, usually bare without its own insulation, which is a safety ground wire. These types of wires are found in BX and Romex /NMD90 cables. Without splitting too many hairs over terminology, that can roughly translate into black meaning “positive” and white meaning “negative”. Remember, we’re talking about AC (alternating current) here.
However, if we’re talking about DC circuits and electronics, quite often you’ll find a red white and a black wire. (Often, but not always …) In the world of DC electronics, the accepted wiring convention is that the red wire carries the positive voltage, and the black is circuit ground. Usually the red is marked as + (plus) and the black is marked as – (minus).
Notice that in both AC electricity and DC electronics, there is a black wire. But in AC electricity the black is hot (“positive”) whereas in DC electronics black is for negative.
Why? Because the worlds of AC power distribution and DC electronics developed somewhat independently, but the fact that both used black wires for different meanings was rarely an issue.
But now that low voltage LED lighting is commonplace, the question of “where to connect the black wire” has become confusing. Essentially, LEDs are a form of DC electronics – another name for LED lighting is SSL lighting, which means Solid State Lighting. As DC electronics, wires attached to LED devices usually (should) conform to DC wiring colour-code conventions.
The issue can arise when installing LEDs using an external power supply/driver, such as with LED strips (tape lights) and LED bars or even pendant lights. On the AC input to the power supply, you need to connect the hot/positive wire to the corresponding input of the power supply. But on the low voltage DC output side (12 – 24 V), the black wire means negative, and the red wire is hot/positive. If the power supply has terminals on the output side instead of coloured wires, the temptation would be to connect the black wire to the + (positive) terminal, and the red to the minus. But, LEDs being polarity-sensitive devices, the light won’t turn on! What’s more, there are even some special LED strips that can be damaged by reverse polarity connection.
AND NOW – we’ve noticed a rather disturbing trend of LED products coming out using white and black wires, with the black wire connected to positive. That’s really confusing. (China, I’m looking at you!) What’s going on?
My best guess is that there are some product engineers out there who want to “do it right” and so they go to trusty google (ok, it’s Baidu in China, as Google is blocked …) to find out what color the wires should be, and where they should be connected. And … they find some article that says black is positive/hot and white is neutral negative. But what’s missing is the fact that info is about AC WIRING only! It doesn’t apply to electronic devices like LEDs.
For LEDs, the red wire should be positive and the black wire negative. That’s it. Black wire should never carry positive in DC wiring. Got it?
FAQs
For LEDs, the red wire should be positive and the black wire negative.
Is black wire usually positive or negative? ›
Typically, if you're looking at a direct current (DC), the black wire is negative. If you're looking at an alternating current (AC), the black wire is positive. That's why it's so important to determine which type of circuit you're looking at before diving into any electrical work.
Which wire is positive and negative on LED? ›
The anode (longer lead) is the positive lead and the cathode (shorter lead) is the negative lead.
Which wire is positive and negative light fixture? ›
Here's how to tell the wire colors apart: The red wire is positive. The black wire is negative. The white wire (if present) is ground (sometimes called neutral in DC).
What happens if you connect a negative wire to a positive wire? ›
If positive to negative on a battery charger are connected, the current will flow, and the device will charge. If the wires in a phone or laptop are reversed, it won't work and may be damaged. Even though both wires are supposed to be hot (carry current), some devices have one side designated as neutral or ground.
How do you tell which wire is hot when both are black? ›
The easiest and safest way is to use a multimeter to test for current.
- Don a pair of protective rubber gloves before testing to find out which black wire is hot. ...
- Set your multimeter to measure voltage. ...
- Place the prong of the multimeter's red wire on the bare metal on the end of one of the black wires.
A wire gauge of 18 AWG or higher is recommended. You should also use a high-quality soldering iron and solder to connect your wires to the LED strips. To power Hit Pro 24V LED strips, you will need a 24V DC power supply that can handle the total wattage required.
What are the three wires on LED lights? ›
In wiring an LED light fixture that has 3 wires to AC household circuit, especially in the USA, the black wire to black wire of the outlet for “Hot”; the white wire to the white wire of the outlet for “Neutral”; and the remaining yellow wire is for the 'ground connection' wire and which is to be connected to either the ...
What happens if I wire a light fixture backwards? ›
One of the main dangers is the risk of electrical shock. When a light switch is wired backwards, it can cause the hot wire to be connected to the neutral terminal on the switch, which can result in the metal parts of the light fixture becoming energized.
What do I connect the black wire to? ›
Power comes from the service panel along the black (hot) wire through other outlets, switches and light fixtures on the circuit and begins its return to the source through the white (neutral) wire. The black wire attaches to a brass terminal; the white wire, to a silver terminal.
Generally, black or red wires are hot, white wires are neutral, and green or bare copper wires are ground. However, standards can vary, so it's crucial to verify before you proceed.
What does black wire mean? ›
A black electrical wire is always considered a hot wire — a wire that carries a live current from the electrical panel to its destination. Black wires generally transfer power to switches and outlets in various circuits and can be used as switch legs, which connect a switch to the electrical load.
What happens if you mix up positive and negative speaker wires? ›
If you connect the positive wire to the negative part of the speaker, the sound wave reverses and travels as an inverted or reversed polarity. It creates destructive interfaces where sound waves often cancel each other and weaken the waves. Hence, some sound frequencies will not be heard in between the audio.
What are wire color codes? ›
The following color codes are typically used in these settings:
- Phase 1: Black wire.
- Phase 2: Red wire.
- Phase 3: Blue wire (used in 208V three-phase systems)
- Neutral: White wire.
- Ground: Green, green with a yellow stripe, or bare wire.
There are also positive and negative cables in the jumper cable set. The red one is positive (+), the black one is negative (-). Never connect the red cable to the negative battery terminal or a vehicle with a dead battery.
Is live wire positive or negative? ›
The positive wire (live wire) carries current from the source to the devices, while the negative wire (ground wire) completes the circuit.
Is white or black wire hot? ›
What do the Different Color Wires Mean? Here's a rundown of electrical wires: The black wire is the "hot" wire, it carries the electricity from the breaker panel into the switch or light source. The white wire is the "neutral" wire, it takes any unused electricity and current and sends it back to the breaker panel.
Does black wire mean live wire? ›
A black electrical wire is always considered a hot wire — a wire that carries a live current from the electrical panel to its destination. Black wires generally transfer power to switches and outlets in various circuits and can be used as switch legs, which connect a switch to the electrical load.
