 Myself, Deshmukh Sachin, working as assistant professor in WALCHAN STRIP TECHNOLOGY, civil engineering department. Today we are going to learn how to measure the pressure by using inverted U2 differential manometer. You know manometers are used to measure the pressure and pressure difference. At the end of this session, you will be able and you can calculate the pressure difference from inverted U2 differential manometer for the same pipe or for different pipes. The inverted U2 differential manometer is going to join for a one pipe or two different pipes. Previously, we have seen that U2 differential manometer, we have joined to a single pipe of whose pressure difference we have calculated and the same we can join to two different pipes of whose pressure difference we are going to find out or we have calculated it. Similar way, inverted it is you can say upward. The manometer is kept upward, a pipe is there and manometer is attached. Can you imagine for which particular liquid which can use, we can use for water also, we can use for gas, we can use for vapor pressure. So particularly this inverted U2 differential manometer, we can see in the industries. And manometric liquid, there will be some question in your mind which manometric liquid will be there because in U2 differential manometer we have seen the liquid was mercury which is a heavy liquid, which is a heavy liquid. Specific gravity is 13.6 for manometer that we are using for U2 differential manometer. Now for inverted U2 manometer, here totally opposite to that that the specific gravity of that liquid must be less than the liquid of flowing liquid, isn't it? So that can be float or that can be above that liquid and which is also the same characteristics which is not going to mix with water or whatever the liquid is flowing. So many characteristics it must have that can be used as a light liquid or we can see the manometric liquid. See the figure, see this figure, concentrate on this figure, previously the U2 differential manometer is like this, now it is totally opposite to it. Now here X line is over here that is a datum line over here, the liquid from this pipe A is pushing this manometric liquid, this manometric liquid comes down, this is the liquid of that second pipe that is pipe B, this is you can say this is the height of this liquid, this is the height of this pipe A liquid, this is the light liquid, this is the difference, this is the difference H, that is a difference of manometric liquid from datum line, from the datum line. In inverted U2 differential simple U2 differential manometer what we have seen this liquid goes up, now this liquid goes down now in inverted U2 differential manometer and similar way that we are going to equate the pressure of this left limb and pressure in the right limb. So from the figure P is the pressure at point A, Pb is the pressure at point B, H is a difference of light liquid level just now we have seen, H1, H2 these are the heights of the water, the liquid above you can say from the pipe below the datum line, rho 1, rho 2 and rho at the density of the liquid of the pipe A, pipe B and the light liquid. We need to calculate the pressure difference between point A and B that is P A minus Pb, P A minus Pb that we now can find out by equating the pressures, pressure in the left limb below the datum line is P A minus rho, now why minus because it is inverted and it is you can say below the datum level it is rho 1 gh1 and pressure in the right limb it is Pb minus rho 2 gh2 minus rho 1 gh1 just see here there are two liquids on the right limb there are two liquids this one as well as this one, this one as well as this one, this one as well as this one. So here on the right limb there are two as pressure is same for the horizontal surface and therefore we will have to following equation to be mentioned here that is on the left arm as well as on the right arm equate this so that we will get the P A minus Pb. So this particular equation we get P A minus Pb is equal to rho 1 gh1 this rho 1 gh1 it goes on the right hand side and remaining both the terms as it is rho 2 gh2 rho 1 gh. Now some important things regarding this inverted duty differential momentum manometer that we have to see this is used to measure the low difference of pressure and which is very accurate also. Second the flowing liquid must have more specific gravity than the manometric liquid isn't it which is totally opposite to the duty differential manometer and for low pressure difference it gives large deflection which is most important to us to calculate the difference. Now as we know this particular concept of this now we will find out the difference of pressure by considering two problems. First one just see the figure and inverted u2 is shown which is used to measure the pressure difference between two points A and B which has water flowing from this the water is flowing from this the water is flowing and this is the you can say manometric liquid is there the difference in level is 0.3 meter and A this A is 0.25 B is 0.15 calculate the pressure difference P a minus P b if the top of the manometer is filled with the oil of relative density 0.8 this is filled with relative density 0.8. So oil is used which is going to float and which is having the specific gravity less than water it is going to float. So equate we know P a minus P b is equal to the pressure in the left limb minus pressure in the right limb. So h is given to us that is 0.3 meter A is 0.25 B is 0.15 rho density of water you can take 1000 kg per meter cube P2 it is that is given to us relative density that is 0.8 or you can say specific gravity then as it is inverted u2 differential manometer we know this is the equation. So P a minus P b if you can put this values you can put this values P a minus P b you will get 0.04 Newton per meter square 0.04 Newton per meter square these are some questions review questions and you can calculate it very fast no problem for that. These are its answers for the first one the answer is 1471 Newton per meter square and we can use for gas as well as for liquid only the thing that the manometric liquid must have the specific gravity less than the flowing liquid and which is not going to mix also. Second problem you can see similar way an inverted u2 differential manometer is there specific gravity is 0.9 it is connected to two different pipes carrying water similar way only on the right hand side we have taken in the that particular deflection here the values are given directly put these values put these values directly in the equation. So P a is also given to you P a is also given to you it is the pressure in the pipe a is 2 meter is given to you put this value over here 2 meters put all this as per the equation P a minus P b. So you will get P b is equal to 1.88 meter in terms of head head of water and in terms of you can say a unit that is kilo Newton per meter square it is 18.44 kilo Newton per meter square 18.44 kilo Newton per meter square particularly you can solve more problems for this u2 inverted u2 differential manometer it is very interesting phenomenon use these books as a references for solving more and more problems if you find any difficulty regarding solving any problem you can contact me. Thank you.