Engineering Question #3464

Roman Tanisis, a 27 year old male from Coquitlam, BC asks on May 26, 2006,

Hi was always wondering if it is ok to use a higher voltage power supply for a lower voltage device. For example if you have a 5V device can you use a 19V AC-DC adapter? I would like to know how this works, if the adapter will deliver at 19V or if it will only deliver at the amount the device requires. I know there is a V=IR relationship so I was thinking maybe the 19V rating was just an average number for output. It is hard to find an answer on google so I was hoping you might help.

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The answer

Barry Shell answered on May 26, 2006

It won't work. You will likely ruin the device you are plugging it into. You have to provide the right voltage or you will burn out one or more components in the receiving device. Voltage is a measure of potential energy. If you deliver 19V to an electrical circuit expecting 5V some of the parts (resistors or transistors, etc.) will get too much energy, then get too hot, and burn up. You might even see some smoke. I would not try it unless you don't care about the 5V device you are going to fry. The adaptor will not lower its voltage to accommodate the receiving device. By the way, you also have to be careful of the polarity. The + or the - sign. Most of this you can learn by asking a salesman at a store like Radio Shack or The Source.

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