As shown in the picture, it is a teapot with exquisite workmanship. There is a small hole on the lid of the kettle to measure the internal and external air pressure when pouring water.

Analysis: Teapots are typical communication equipment. When the water does not flow, the liquid level in the spout and the pot body should be flush, and the small hole in the lid plays the role of communicating the air pressure in the teapot with the atmospheric pressure.

The small holes on the pot cover are communicated with the inside and outside air, so that the air pressure inside and outside the pot is equal, and the water in the pot can be poured out in turn; The kettle body and spout form a communication device, because the water level is flat when the water is still, so the height should be the same when making.

So the answer is: equality, connector.

Comments: Teapots are common daily necessities, which contain the knowledge of connectors and atmospheric pressure, and deserve our attention, especially the small holes on the teapot cover, which play an important role here and cannot be ignored.