The pressure measured in terms of the atmospheric pressure by taking it as absolute zero is called a gauge pressure and hence it is a difference between actual pressure and atmospheric pressure.
The gauge pressure is positive if the pressure measured is above the atmospheric pressure and is negative if it is below the atmospheric pressure. Here is a list of gauge pressure example that we are going to discuss in this topic:-
Manometer
The manometer is used to measure the pressure in different systems. It is also used to measure the blood pressure of the patients. It is filled with liquid with one or two ends open. The pressure felt at one end of the tube will push the liquid such that it will raise the height of the liquid on the other hand while decreasing the height on the nearest end where pressure is exerted on the liquid.
At atmospheric pressure, the pressure inside the tube is read as null and the liquid does not move, the gauge pressure is positive when the pressure is experienced on the liquid otherwise it is at the absolute zero point.
Pipeline
Inside a pipe, there is pressure due to the flow of water or any liquid carried through the pipeline otherwise it’s a vacuum. The absolute pressure inside a pipe is the sum of the atmospheric pressure and the pressure of a flow. The gauge attached to measure the pressure inside a pipe will read the atmospheric pressure as zero and will measure the pressure of a flow in a pipe which is gauge pressure.
Pressure Cookers
The pressure inside the cooker is generated due to the accumulation of the vapor upon supplying heat energy to the cooker.
The boiling temperature of the liquid increases as the pressure inside a cooker is higher than the normal atmospheric pressure. The gauge pressure is the vapor pressure inside the cooker and the atmospheric pressure is nullified.
Tap
Tap has a meter to read the volume of water utilized by the users to ease the water bill payments. The gauge meter attached to the pipe is used to measure the flow of volume of water through a pipe. It actually works on the pressure exerted on the gauge due to the flowing water.
Gas Cylinders
The cylinders are filled with liquid petroleum gas and maintained under a pressure greater than atmospheric pressure.
When the knob is opened, the liquid phase is converted into the gaseous state on overcoming the high-pressure conditions and this gas runs through a pipe to the burner. The gauge pressure in this case is independent of the atmospheric pressure inside a cylinder.
Compressors
The compression is caused when the equal and opposite forces are exerted on the body from at least two directions. It results in the reduction of the molecular spaces within the object. The gauge pressure is the force exerted on the unit area of the object and is obviously positive as the pressure impose is greater than the atmospheric pressure.
Cartesian Diver
It is a small toy where a toy diver is inserted into a bottle of water and it remains floating on the top layer of water with half dip inside until the force is imposed on the surface of the bottle then it dips and reaches the bottom surface of the bottle.
This happens because the molecular force exerting on the surface of the bottle from both sides is canceled out upon putting the pressure on the bottle and the only force that comes into action is the force from the knob of the bottle above.
Water Pumps
The water through a pipe runs because of the pressure difference. The water moves from the high-pressure area to the low-pressure region.
The pump is used to apply the pressure greater enough than the pressure of the water flow to push or pull the flow of water through a pipe. The gauge pressure is more than the atmospheric pressure and hence is positive.
Deep-Sea
The seawater is a mixture of different salts and minerals and the pressure is almost thrice that of the atmospheric pressure. The gauge pressure is positive beneath the surface of the seawater. Under this pressure, it becomes difficult for sea divers to breathe in and hence carries oxygen cylinder while diving.
Bicycle Pump
It is used to fill the air in the tires of the bicycle. The pressure gauge attached to the pump will read the pressure inside the tire on connecting to the tire to pump the air. The pressure of the gas inside the tire will keep on increasing as the molecular pressure rises with an increasing volume of the gas inside the tube.
After filling the air in a tire and as you separate the pump from the bicycle tire, the pressure gauge should read the atmospheric pressure but it pressure gauge read zero pressure point after disconnecting. The atmospheric pressure is taken as the absolute null point of the pressure gauge and hence it read the atmospheric pressure as zero.
Wind Pressure
The gauge can be used to measure the wind speed by calculating the pressure exerted on the object. The gauge will calculate the pressure due to the wind force exerted on the unit surface area of the object relative to the atmospheric pressure. The gauge will read atmospheric pressure as a null pressure and hence we can estimate the wind pressure.
Oxygen Cylinder
The oxygen is stored in the cylindrical container in the form of a liquid state maintained at high pressure. To measure the pressure inside this cylinder, the cylinders are attached to the pressure gauge.
By opening the knob of the cylinder, the oxygen is converted into the gaseous form due to pressure difference and flows through the pipe to the oxygen mask attached to the pipe.
Soft Drink Bottles
The soft drinks are preserved by packing the bottles and inserting the carbon dioxide gas. You must have observed the effervescence in the soft drinks immediately after opening the bottle of soft drinks or soda bottles; this is because the pressure created in the bottle due to these gas molecules is released on removing the cap over the bottle.
Boilers
The pressure gauge is used to measure the pressure due to the boiler that is used in many industries. The pressure is generally created because of the evaporated steam due to the boilers as the immense heat is utilized to break the bonds between the molecules and convert the liquid phase into the gaseous phase.
Fire Extinguisher
The pressure inside the cylinder is due to the carbon dioxide gas stored in it that is released during emergencies to extinguish the fire. The pressure inside the cylinder is around 185-195 psi and is gauge pressure excluding the atmospheric pressure in which the cylinder is present.
Frequently Asked Questions
How to measure the gauge pressure from the absolute pressure?
We can measure the gauge pressure using the formula
Pgauge=Pabs-Patm
The absolute pressure is the sum of the atmospheric pressure and the gauge pressure exerted on the system at constant atmospheric pressure, hence we can calculate the gauge pressure using the formula given above.
What is relative pressure?
It is the pressure relative to the atmospheric pressure.
The relative pressure is the pressure higher or below the atmospheric pressure with respect to the atmospheric pressure condition taking it as a null pressure point same as the gauge pressure.
Also Read:
- Negative pressure example
- Absolute pressure example
- Dynamic pressure example
- Relative pressure example
- Hydrostatic pressure example
- Pressure in dynamic equilibrium
- Osmotic pressure example
- Freezing point and vapour pressure
- Does viscosity change with pressure
- Ocean pressure example
Hi, I’m Akshita Mapari. I have done M.Sc. in Physics. I have worked on projects like Numerical modeling of winds and waves during cyclone, Physics of toys and mechanized thrill machines in amusement park based on Classical Mechanics. I have pursued a course on Arduino and have accomplished some mini projects on Arduino UNO. I always like to explore new zones in the field of science. I personally believe that learning is more enthusiastic when learnt with creativity. Apart from this, I like to read, travel, strumming on guitar, identifying rocks and strata, photography and playing chess.
