Options: the pressure is the same as that outside, normal atmospheric pressure is maintained by the use of air pumps, the pressure inside is less than the pressure outside, normal humidity and partial vacuum are maintained
Benjamin Franklin was a prolific inventor. He invented the lightning rod, the Franklin stove, studied electricity, discovered the Gulf Stream, started the first library, and on and on. Among his many other inventions, what musical instrument did he invent?
Options: the densities of the liquid in the two vessels are equal, the level of the liquid in the two vessels are at the same height, both its limbs are of unequal length, the temperature of the liquids in the two vessels are the same