What Color Is Positive And Negative

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When you're dealing with electrical wires, it's important to know which wire is positive and which is negative. While some wires will come clearly marked with a plus (positive) or minus (negative) sign, others aren't quite as clear. For those unmarked wires, you can first try to identify the polarity by looking at physical characteristics like color or texture. If you still aren't sure, test your wires with a digital multimeter. Then, let there be power!

1

Know that appliance plugs don't really have positive and negative sides. They have "hot" wires and "neutral" sites, instead.^[1]
2
Note that a ribbed wire is usually the negative wire on an extension cord. If you have a wire where both sides are the same color, which is typically copper, the strand that has a grooved texture is the negative wire. Run your fingers along the wire to determine which side has the ribbing.^[2]
- Feel the other wire which is smooth. This is your positive wire.
3
Identify the black positive wire on a ceiling light fixture. When you're hanging a chandelier or any other ceiling light, first find the 3 wires coming out of the hole in the ceiling where the light will go. Recognize that the black wire is the positive one, the white wire is the negative one, and the green wire is the ground.^[3]
- You may see a copper wire instead of a green wire for the ground.
4

Know that the copper wire is usually positive on a speaker wire. On a standard wire used for things like speakers and amps, the silver strand is the negative wire and the copper-colored strand is the positive wire. These wires are often held together by a clear casing, so they're easy to determine the polarity of each side quickly.^[4]

Different Wire Color Scenarios

If the multi-colored wire is black and red, the black wire is the negative wire, while the red one is positive.

If both wires are black but one has a white stripe, the striped wire is negative, while the plain black wire is positive.^[5]
5
Look in the owner manual to determine which wires are negative in a car. Every car follows its own color-coding system for wires. There is no standard or international system, so find the wiring diagram specific to your make and model in your owner manual.^[6]
- If you no longer have your manual, look for one in a library or online. Or, reach out to a mechanic at a local shop or dealership.

1
Put your digital multimeter on the direct current voltage setting. Rotate the selector switch, which is the large knob in the center of the multimeter, to the symbol which looks like a capital "V" with a straight line over it. This is the direct current (DC) voltage setting of your multimeter.^[7]
- Do not use an analog multimeter to test polarity. Connecting the wrong leads to the wrong wires can damage an analog multimeter.
2
Attach 1 lead to each wire to connect the wires to the multimeter. For now, it doesn't matter which lead you connect to which wire. Clip the small alligator clip on the red lead to the end of 1 wire and the clip on the black lead to the end of the other.^[8]
- Check that the black lead is plugged into the port on the front of the multimeter labeled "COM." Plug the red lead into the port labeled with the volt symbol, which is "V."
3
Look at the reading to see if it's a positive or negative number. Once you attach the leads to the wires, check the number on the screen of the multimeter. This is the voltage of your wire, and can be either positive or negative. ^[9]
- If there is no reading, first check that the alligator clips are tightly secured to the wires.
- If you still aren't seeing a number on the screen, replace the batteries in your multimeter and try it again. You may need new leads if there's still no reading.
4
Note that the wire on the red lead is positive if the reading is positive. If your multimeter has any reading that's a positive number, like 9.2 for example, the leads are connected correctly. This means that the wire hooked to the red lead is positive and the wire hooked to the black lead is negative.^[10]
- If your multimeter has a negative reading, like -9.2 for example, the leads are reversed, which means the red lead is hooked to the negative wire.
5
Switch the leads so the red one is now on the other wire if there's a negative reading. Reverse the leads, clipping the red lead to the wire that the black lead was connected to and vice versa. Once you flip them, look for a positive reading to verify that the leads are placed on the correct wires.
- For instance, check that a reading of -9.2 becomes 9.2.
- If the reading is still negative, you may have a faulty multimeter. You can take it to an electronics store to have the fuses checked, or buy a replacement.

Add New Question

Question

If two wires are black, how can I tell which is negative and which is positive?

Ricardo Mitchell
Electrician & Construction Professional, CN Coterie

Ricardo Mitchell is the CEO of CN Coterie, a fully licensed and insured Lead EPA (Environmental Protection Agency) Certified construction company located in Manhattan, New York. CN Coterie specializes in full home renovation, electrical, plumbing, carpentry, cabinetry, furniture restoration, OATH/ECB (Office of Administrative Trials and Hearings/Environmental Control Board) violations removal, and DOB (Department of Buildings) violations removal. Ricardo has over 10 years of electrical and construction experience and his partners have over 30 years of relevant experience.

Electrician & Construction Professional, CN Coterie

Expert Answer

Use a multimeter to test each one. Put the red side on the terminal to one black wire and the black side of the terminal to the other wire. If the tester shows voltage, the wire touching the red terminal is the one that has power.

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Reversing the polarity in a circuit can ruin the power source or even cause an explosion.
Connecting the wrong wires, like using a positive wire when it should be a negative wire, can also fry the wires themselves.
Never use an analog multimeter if you aren't sure which wire is positive vs. negative. Hooking up the wrong polarity to the wrong leads could damage the multimeter.

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Article SummaryX

If you want to identify positive and negative wires, keep in mind that appliance plugs have hot wires and neutral sites, rather than positive and negative sides. However, if you're using an extension cord, the positive wire will be the smooth one, while the negative wire will have a ribbed or grooved texture. To find the right wires on a speaker, check to see which colors you have. For example, negative silver wires are paired with positive gold wires. Alternatively, if you have a black wire, it'll be negative if the other wire is red, or positive if the other wire is striped. For more tips, like how to use a digital multimeter to identify positive and negative wires, scroll down!

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