 Myself Sachin Deshmukh working as assistant professor in the department of civil engineering of Vyalchand Institute of Technology, Solapur. Today we are going to learn the measurement of pressure by YouTube differential manometer. It is one of the equipment or you can say small instrument by which we are going to measure the pressure. At the end of this topic you are able to calculate the pressure difference between two points in the same pipe if it is the same pipe and from different pipes. You are going to find out the pressure difference of two different pipes or one pipe where you can attach the YouTube at two points. We will see what is the YouTube differential manometer. It is a device which is used to measure the difference of pressure between the two fluids which are flowing through the two different pipes or in the same pipe at different points is known as YouTube differential manometer. The important two types are one is YouTube differential manometer and second is inverted YouTube differential manometer. Particularly inverted YouTube differential manometer we are using to find the pressure difference of gas. Here we are seeing this YouTube differential manometer at same level as well as at different level. First we will see the YouTube differential manometer. It consists of a YouTube both the ends are attached to the pipes. These are two different pipes. This is the center of pipe. This pipe is A. This center of pipe this is B. These two points are at same level. This is called as a left limb or left arm. This is called as a right limb or right arm. The liquid level of this left arm is x plus h which is not given separately. But we can calculate this is x plus h. This is the liquid level of this particular flowing liquid. That of B you can say x is the only liquid level of liquid which is flowing through this pipe. Now this red is a manometric liquid. The lowest level from here it is a datum level. And when it rises up this h it is a manometric head you can say h is a head of the manometric liquid. Particularly for YouTube differential manometer we are using mercury because of its many characteristics that is having the highest specific gravity that is 13.6. Then it is a sparkling then it is not going to adhere to any of the wall in contact and it is not going to mix also. And whenever the temperature differences are not going to measure not going to hamper it more on this mercury that is why we are using mercury as a manometric liquid. This is for the pipes at same level. Similarly we are going to find out the pressure head or difference of pressure head when the two pipes are at different level. This is pipe A or center of pipe A, the center of pipe B. They are at two different level. This is the liquid level of fluid which is or liquid which is flowing through this pipe. This is of y is a flowing liquid or height of flowing liquid which is passing through or flowing through this pipe B and similarly the this is a manometric liquid mercury we are taking manometric liquid. And one more thing just keep in your mind whenever there is a u tube differential manometer we are going to measure the heads above this x axis and when it is inverted this figure is totally opposite to this. Then we are going to measure the heads below x axis for inverted. So first we will calculate the u tube differential manometer at the same level and from this we can calculate the difference of head these are the notations h difference of mercury level x is the distance of center of A from the mercury level of the left limb. S1 specific gravity of the liquid which is flowing through pipe A, S2 is the specific gravity of the liquid which is flowing through pipe B, S is the specific gravity of manometric liquid or the heavy liquid that is mercury, HA is the pressure head at A and HB is the pressure head at B. We know that pressures in the left limb and right limb above the datum must be equal that is equilibrium condition and when the equilibrium condition arises then and then only we can find out the pressure differences. Now pressure head in the left limb it is pressure head at A plus x plus h this is the total head of the specific gravity S1 liquid or the liquid which is flowing through the pipe A. Similarly pressure head in the right limb HB plus x into S2 x is the height of the liquid from left limb, right limb plus h that is the manometric head into the specific gravity of the manometer S it is 13.6 equating these two we get HA minus HB is equal to x into S2 plus h into S minus x plus h into S1. Many times it happens that both the liquids are same at that time S1 is equal to S2 and then calculate. Now we will see for the second case that is YouTube differential manometer at different level same notations are there H difference of mercury level in the YouTube x distance of center of A from mercury level of the left limb y then S1, S2, S, HA and HB same notations here also when the equilibrium condition arises then and then only we are going to find out the difference of pressure in the fluctuating case we cannot find the pressure difference. Now equating this equation that is the total pressure head in the left limb and total pressure in the right limb we will get the pressure difference. See here pressure head in the left limb is HA plus x plus h into S1 I will show you here x plus h this x plus h into S1 specific gravity of this one this is in the left arm or left limb simultaneously on the right limb what it comes the y into S2 comes correct y into S2 comes and H into S specific gravity of this manometric liquid the pressure head on the left limb equal to pressure head in the right limb that we have to put see here HA plus x plus h into S1 similarly on the right limb HB plus y into S2 plus h into S equating these two HA minus HB we get y into S2 plus h S minus x plus h into S1 whenever the liquids are same specific gravity you have to equate S1 is equal to S2 and then you can calculate these two equations are for YouTube differential marometer when they are at the same level the pipes are at the same level as well as the pipes are at different level for inverted what happens inverted the total scenario is you can say change and the YouTube is inverted YouTube and particularly this inverted YouTube marometer we are using to find the difference of pressure of the gases now pause the video and answer the questions manometers are the pressure measuring devices which use the principle of dynamic pressure to measure the pressure difference you have to say true or false and differential manometers gives the pressure reading with respect to atmosphere pressure that also you have to say that it is true or false both are false manometers are the pressure measuring devices which use the principle of dynamic pressure to measure the pressure difference no it is wrong and differential manometer gives the pressure reading with respect to atmosphere pressure this is also wrong statement solve some more problems with this reference books