If UNO is supplied with 9VDC to Power Jack. Will it supply power to USB connector?

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As you can see in the schematic, the USBVCC is only connected (via a MOSFET) to the 5V line, when the voltage on VIN (barrel jack) is LOW.

If you connect 9V to the power jack, the mosfet will turn of, and disconnect the USB power from the 5V on the UNO.

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