 My name is Saurabh Deshmukh, working as an assistant professor in Department of Mechanical Engineering, Vulture Institute of Technology, Sallapur. In this video, we are going to learn the YouTube Manometer used as gauge pressure and for vacuum pressure. Also, we will see the problems on it. The learning outcomes. At the end of this session, the learner will be able to explain YouTube Manometer and will also be able to solve problems on it. These are the contents. First of all, we will see the YouTube Manometer used for measuring the gauge pressure and also for vacuum pressure. We will also see the problems on YouTube Manometer. So we all know the manometers are used for measuring the pressures at a point in a fluid by balancing the column of fluid by same or any other fluid. So these manometers are the pressure measuring devices. So we will now see the YouTube Manometer. So YouTube Manometer can be used for measuring the gauge pressure or for vacuum pressure. Now we will first see for the gauge pressure. So I will draw first the diagram of YouTube Manometer used for measuring the gauge pressure. So this will be the pipe in which we are going to measure the pressure of the fluid. It is connected to a YouTube Manometer. So in this pipe, we will feel the fluid of which the pressure is to be measured. And in YouTube Manometer, actually it consists a glass tube bent in U shape. One of its end which is connected to the point at which the pressure is to be measured. So this end is connected to a pipe in which we are going to measure the pressure and the other end remains open to the atmosphere. Also we feel this YouTube by the fluid which has greater specific gravity than the liquid whose pressure is to be measured. So this is a light liquid and in this we will feel the liquid with higher specific gravity. So what happens? With the high pressure in this pipe, the fluid flows to the YouTube and the mercury level either we can use the mercury or any other liquid which is having the higher specific gravity. So the mercury level in the right limb will increase. Today we will consider this as a datum line, we will consider it as XX. So this will be the level of mercury in left limb and this is the level of mercury in right limb. So the height of rise in the right limb will be H2 and from the center of the pipe to the level of mercury in left limb, this height will take as H1. Suppose now this fluid of which the pressure is to be measured has density rho1, rho1 will be density of light fluid, rho2 will be density of heavy fluid. H1 is height of light liquid above the datum line up to the center of the pipe. So it will be H1, H2 will be the height of heavy liquid above the datum line in right limb. So now as we achieve the equilibrium of the pressure above XX, otherwise what will happen if the pressure either one of the side is larger then the fluid will flow in that direction. So we maintain the height of mercury in the left limb at H2. So what we have achieved here, the equilibrium of pressure above XX. So we will equate pressure above datum line XX. So what will happen, consider the pressure in this pipe as P. So in the left limb, what are the pressures here? The first pressure is P plus pressure due to pressure height H1 or pressure head H1. So what will it be, rho1 g H1 equals to the pressure in the right limb. So what is the pressure in right limb, rho2 g H2. So we know the rho1 g is constant 9.81, height we can get by observation H1, rho2 we know the specific gravity or the density of the heavy liquid, g is 9.81 and H2 we can observe it on the marking of the U2 magnet. So we can easily find out the pressure P in the pipe. This is for gauge pressure. Now for vacuum pressure, the construction is same. For what happens in vacuum pressure, the level of heavy liquid in the manometer in the right limb will decrease as the pressure in the pipe is lower. So atmospheric pressure is high. So what will happen, from high pressure to low pressure, the mercury will flow. So this will be the fluid of which the pressure is to be measured. From this, the height of mercury will start. So the height of mercury level in right limb will decrease. Now we will consider this as a datum line. So this will be xx. So H1 will be the height of light fluid and H2 will be the height difference of the mercury in two limbs. In this condition also we will achieve the equilibrium pressure. So the pressure at left limb equals to pressure at right limb. So now consider the pressure in the pipe will be P plus the pressure due to this pressure head H1. It is rho1g H1 plus due to pressure head H2. It is rho2g H2 equals to we consider atmospheric pressure as zero datum pressure. So it will be zero in left limb. So we can easily calculate the value of P for vacuum pressure. Now we will see the problems on this. Now we will see the problem of the YouTube manometer that is used for measuring the gauge pressure. So the right limb of a simple YouTube manometer containing mercury is open to the atmosphere while the left limb is connected to a pipe in which a fluid of specific gravity 0.9 is flowing. So this is the pipe through which a fluid is flowing having specific gravity 0.9. The center of the pipe is 12 centimeter below the level of mercury in right limb. So this is the center of the pipe below the 12 centimeter of the level of mercury in right limb. Now find the pressure of the fluid in pipe if the difference of mercury level in the two limbs is 20 centimeter. So this will be 20 centimeter. Now we consider this datum at AA. So what are the given data here? First of all the specific gravity of fluid of which the pressure is to be measured. It is 0.9 so we will consider it as S1 equals to 0.9. So what will be density of that fluid? It is 1000 into S1 which is equals to 900 kg per meter cube. Also they have said that the YouTube manometer containing mercury. So what is the density of mercury here? Rho 2 equals to 13600 kg per meter cube. Also they have said that the center of the pipe is 12 centimeter below the level of mercury in right limb. So this is 12 centimeter and also the difference of mercury level in two limbs is 20 centimeter. So what is it is called as it is H2 we consider it as H2. So H2 equals to 20 centimeter which is equals to 0.2 meter and what will be H1 here? H1 is nothing but the height of fluid in left limb. So this will be H1. Its value will be 20 minus this is 12 which is equals to 8 centimeter which is 0.08 meter. Now we will equate the pressure above AA. So we will equate the pressure above AA equating pressure above datum line AA. So what it will be? We will consider the pressure in the pipe will be P plus here this is H1. So Rho 1 G H1 equals to Rho 2 G H2. Therefore P that is we are going to calculate plus Rho 1 is 900 into G 9.81 multiplied by H1 is 0.08 equals to Rho 2 is 13600 multiplied by 9.81 into what is the H2 it is 0.2. So after calculating this equation we will get P equals to 25976.8 Newton per it is centimeter square or we need to convert it into the meter square. So it will be P equals to sorry it is Newton per meter square and after converting it to the centimeter we will get 2.5976 Newton per centimeter square. These are the references. Thank you.