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When we press the bulb of a dropper with its nozzle kept in water, air in
the dropper is seen to escape in the form of bubbles. Once we release the
pressure on the bulb, water gets filled in the dropper. The rise of water in
the dropper is due to
(a) pressure of water
(b) gravity of the earth
(c) shape of rubber bulb
(d) atmospheric pressure
Answer
(d) atmospheric pressure.
Water rises in the dropper due to atmospheric pressure.
When bulb is pressed, air present in tube and bulb escapes in the form of bubbles.
Due to this, Pressure inside bulb decreases
However, there is atmospheric pressure on surface of liquid.
When we release the bulb, the water moves inside the tube.
Water moves from higher pressure (from water kept) to lower pressure (inside the glass tube).
