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What Is a Positive Terminal?

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  • Written By: Paul Scott
  • Edited By: R. Halprin
  • Last Modified Date: 15 April 2014
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    Conjecture Corporation
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The term positive terminal describes which of the two connection terminals on direct current (DC) equipment supplies or is meant to receive a positive electrical charge. DC power supplies always feature a positive to negative electron flow and always have a negative and positive terminal. Most DC appliances or machines also have a positive and negative terminal which should always be connected to terminals of same orientation on the power supply. Failure to do so can cause severe damage to the equipment and power supply. This positive/negative relationship is commonly known as the polarity of a supply or device.

Any source of direct current electrical power flows from a positive source to a negative source. This applies to the DC side of rectified alternating current (AC) power supplies, batteries, and solar panel outputs. Each of these DC power sources feature a positive terminal and a negative terminal. The permanent relationship between positive and negative sides of DC power supplies is referred to as the polarity of the supply. Power supplies and appliances typically include a ground or earthing connection as well; this has nothing to do with the supply of power or the polarity of the device, however.

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The universal color code and symbol for a positive terminal is red and a plus (+) sign. The color code and symbol for a negative terminal is black and a minus (-) sign. The polarity relationship, color codes, and symbols for positive and negative terminals are also used on the devices powered by DC power supplies. The connection terminals on DC power supplies and devices will always be marked with one or both of these identifiers. When connecting DC devices to a power supply, it is crucial to observe the correct polarity. In other words, the positive terminals on the supply and device should be connected to each other with the same applying to the negative terminals.

In some cases, reversal of polarity can be used to change the direction of operation for some devices and may be included in the controls as a design feature. Some types of resistive DC appliances such as heaters lack specific polarity requirements and will have no markings on their terminals. Generally, DC devices are polarity specific; failure to observe correct polarity will result in damage to the device and the power supply. This applies to all polarity dependent DC appliances devices including loud speakers, motors, capacitors, and electronic equipment.

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Discuss this Article

SarahSon
Post 2

It seems like I am always putting in the wrong side of the battery when I am replacing batteries in something. One time I stuck four rechargeable batteries into a battery pack and plugged it into the wall.

I didn't pay any attention to the light or even realize that they didn't go in very easy. The next day when I went to get the batteries, I was frustrated that none of them were working.

It was not until then that I realized I had put the positive battery side in the wrong way on every one of them.

myharley
Post 1

You will know right away if you don't have the right cable connected to the proper terminal. This was a learning experience for my daughter when her car would not start.

She carried a set of jumper cables with her in the trunk of the car, but somehow the dome light was left on in her car and it would not start the next morning.

She was trying to take of this by herself, but she hooked up the wrong end of the cable to the car battery positive terminal. Obviously nothing happened, and she didn't know what else to do so called someone for help.

She was pretty embarrassed when she realized what she had done, but will never let that happen to her again.

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