Question

water does not run out of a dropper unless its rubber bulb is pressed.
explain.

Answer 1

present when filling up a dropper u press which means you are pushing out all the air present inside  which means u r creating a vacuum .now pressure difference is created and water rushes inside so that so that pressure inside it equals the atmosphiric pressure as there is no pressure difference is there the water stays inside .now to take out the water u need to apply external pressure so that the high pressure is created and water comes out naturally