Submarines: How They Work - Boyles' Law

Text Version

Boyles' Law is that under a constant temperature, gas will compress as pressure is applied. The volume of a fixed amount of gas is inversely proportional to the total amount of pressure applied. If the pressure doubles, the volume shrinks to half.

Pressure is defined as weight per area, usually pounds per square inch. Atmospheric pressure is caused by the weight of the air on each square inch. It decreases with height because there is less air pressing down on a square inch at greater altitudes.

Going into the water, the pressure is determined by the weight of the atmosphere and the water above. Water is about 1000 times more dense than air at the sea surface, so a depth of only 33 feet is equivalent to two times normal atmospheric pressure.

An amount of air at higher altitudes is less compressed and therefore takes up more volume than air at sea level. A balloon inflated and tied off at sea level will expand as it rises in the atmosphere.

Because pressure increases with ocean depth, air is compressed and takes up less volume than at sea level. A balloon inflated and tied off at sea level will compress as it descends in the ocean.

At the water's surface, a diver's lungs is experiences normal pressure exerted upon it.

At 33 Feet (1st Atmosphere), there is twice the amount of air within the diver's lungs. The lung's size remains the same, but the air compresses and doubles in amount.

Because pressure increases with depth, a diver's lungs hold 3 times the amount of air as they do on the surface at 66 Feet (2nd Atmosphere).

At 99 Feet (3rd Atmosphere), a diver's lungs hold 4 times the amount of air as they do on the surface.