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There is some unknown factor here. I need to use an LED to light an area of a device. The device has a 12V, 6A power supply. I was expecting to have to reduce the current from 6A in order to use the 12V LED but the LED is working as -is, connected directly to the 12V, 6A supply. How can this be? I expected the LED to get hot or to burn out. It isn't even getting warm. I'd like to know why.

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Power supplies don't push current; loads pull. 6A is the maximum current that the supply can provide, but it's perfectly happy to supply less. If you have a load that's rated for 12 volts and you attach it to that supply (or any other 12 volt source) it will draw the current that it needs.

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  • \$\begingroup\$ It's this kind of answer with explanation that newbies like myself really appreciate, to drive home the basics before bad thoughts happen to us =) \$\endgroup\$ – Patrick Hughes May 17 at 20:13
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The LED already contains the appropriate resistor to reduce the current to an acceptable level given a 12V power supply.

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  • \$\begingroup\$ Logical, there are no details on the LEDs. Should they not get warm due to the resistor? \$\endgroup\$ – KayBee Jul 31 '15 at 22:23
  • \$\begingroup\$ 12V times 20mA is 240mW. That is true regardless of the resistor. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 31 '15 at 22:25
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You had to connect a 12V LED directly to 12V! There is a build in resistor, so the current will be fine.

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