Figure 14. One-dimensional duct showing control volume. When streamlines are parallel the pressure is constant across them, except for hydrostatic head differences (if the pressure was higher in the ...
The Irish scientist Robert Boyle investigated the relationship between pressure and volume in the 17th century. He trapped a bubble of air at the sealed end of a J-shaped tube using liquid mercury.
Charles’ Law states that if a gas is heated up and the pressure does not change, the volume will. So, for a fixed mass of gas at a constant pressure, volume ÷ temperature will remain the same.