Can u use a digital camera for a webcam?

Yes, it should have it listed in the index of your owner's manual how it is hooked up, some brands cannot be used as a webcam.

NO

yes or at least some of them can be used

If a digital camera shuts down its camera function when connected to a usb port, and identifies the device as a mass storage device, it cannot be used as a web cam. Whereas cameras like Sony Handycam(DCR-TRV 33E) and other similar models can be turned into a web cam by pointer the selector to the camera point when connected to usb and installing the usb driver(manually) from the CD provided. This feature has although NOT been listed in the manual.