News1 min ago
external hard drive
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does a usb external hard drive get its power from the usb cable
thanks gary
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For more on marking an answer as the "Best Answer", please visit our FAQ.USB ports can give +5v, which is enough to power some devices, including an external hard drive using a 2.5" style laptop hard drive, but as gen2 says, this isn't enough to power everything. It's quite rare that external hards drive using a 3.5" (desktop style) can be powered solely by the output from the USB port, usually they have a seperate power supply unit, like a laptop power supply.
I'm not sure how Macs and PCs compare - the voltage is standard at +5v across all USB, but the power (amps / milliamps) doesn't seem to be.