 Hello friends, my name is Saurabh Deshmukh, working as an assistant professor in Department of Mechanical Engineering, Vulture Institute of Technology, Sallapur. In previous video, we have learned the dynamic viscosity along with kinematic viscosity and their units. Also, we have learned the Newton's law of viscosity. In this video, we are going to learn the effect of temperature on viscosity along with its problems. The learning outcome at the end of this session, the learner will able to explain viscosity and will also able to solve problem on viscosity. Now, we will see the viscosity variation along with temperature. So, effect of temperature on viscosity. So, the temperature affects viscosity. The viscosity of liquid decreases with increase in temperature, while the viscosity of gases increases with increase in temperature. So, I will write it here, the temperature viscosity for fluid for gas, ok. So, as the temperature of the fluid or the liquid decreases, as the temperature of the fluid or liquid decreases, the viscosity increases, ok. And as the temperature of the gas decreases, the viscosity also decreases or in other term as liquid and gas, as the temperature of the liquid or fluid increases, the viscosity decreases. And as the temperature of gas increases, the viscosity also increases. This happens because in liquid, the cohesive forces are dominant over the molecular transfer or molecular moment transfer. So, as the temperature increases, the cohesive forces decreases. So, the viscosity, we know that in liquid, the cohesive forces are dominant over the molecular moment transfer. So, as the temperature increases, the cohesive forces decreases, which cause the decrease in viscosity. But in gases, the cohesive forces are smaller as compared to the molecular moment transfer. So, with increase in temperature, the molecular moment transfer increases and hence the viscosity also increases, ok. So, for liquid, mu equals to mu 0 into 1 upon 1 plus alpha t plus beta t square, where the mu is the viscosity of liquid at t degree Celsius, ok. mu 0 is viscosity of liquid at 0 degree Celsius. Alpha and beta are the constants for the liquid, where alpha equals to 0.03368 and beta equals to 0.000221, ok. And the mu 0, that is the viscosity of the liquid or particularly water here, it is 1.79 into 10 raise to minus 3 poise. And for gases, the formula is mu equals to mu 0 plus alpha t minus beta t square, where again mu is the viscosity of the gases at temperature t, mu 0 is viscosity of gases at temperature 0, alpha and beta are constant and t is temperature, ok. For air, the value of mu 0 equals to 0.000117 and alpha equals to it is 0.00000056 while beta equals to it is 0.1189 into 10 raise to. Now, we will see a problem on viscosity. So, the problem a plate 0.025 mm distance from a fixed plate moves at 60 centimeter per second and requires a force of 2 Newton per unit area, that is 2 Newton per meter square to maintain this speed, ok. Now, we need to determine the fluid viscosity between the plates. Now, I will just draw a diagram here, ok. This is the fixed plate and moving plate is at a 0.025 mm distance from the fixed plate. So, this will be the moving plate, which is moving with the velocity 60 centimeter per second, ok. And force is also required here to maintain this speed, which is 2 Newton, ok. And the distance between these two plates is, we take it as a dy equals to 0.025 mm. Let consider these fluids are apart from each other by the means of oil. So, now, we need to calculate the viscosity of this oil, ok. So, first of all, we will write the given data here. So, they have given the distance between the plates, ok. That is dy equals to 0.025 mm, which is equals to 0.025 into 10 raise to minus 3 meter. Also, the velocity of the moving plate is also given, which is u equals to 60 centimeters per second. So, it is, it will be 0.6 meter per second. So, the force on the upper plate also is given. So, that will be F equals to 2 Newton per meter square. Now, we need to calculate the viscosity of the oil, ok. That will be mu equals to tau upon dou u by dou y. So, we have the value of tau here, that is force required per unit area, that is tau, that is shear stress. We also have the value of dy. Now, we need to calculate the du, that is this, that is the difference between the velocities of two plates. Obviously, this velocity, this plate is fixed. So, the velocity of the fixed plate will be 0. So, du equals to, it will be 60 minus 0, which is equals to 60 centimeter per second, that is 0.6 meter per second. So, we will substitute this given data in this formula. So, mu equals to tau is 2 upon du is 0.6 by 0.025 into 10 dash 2 minus 3. So, after calculating this substitutions, we will get mu equals to 8.33 into 10 dash 2 minus 4 poise or either 8.33 into 10 dash 2 minus 5 Newton second per meter square. A flat plate of area 1.5 into 10 dash 2 6 mm square is pulled with a speed of 0.4 meter per second, related to another plate located at a distance of 0.15 mm apart from it. Find the force and power required to maintain the speed if the fluid separating them having viscosity 1 poise. Now, we will write the given data here. So, they have given the area of plate. So, that will be A equals to 1.5 into 10 dash 2 6 mm square, which is equals to 1.5 meter square. Now, they have given the relative speed between the two plates. It is given as 0.4 meter per second. So, it will be du equals to 0.4 meter per second. They have also given the relative distance between the two plates that is 0.15 mm. So, it will be dy equals to 0.15 mm, relatively 0.15 into 10 dash 2 minus 3 meter. So, now we need to calculate the force required and power required to maintain the speed. So, we know that tau equals to mu into du by dy. So, we will first calculate the tau that is shear stress. So, it will be also they have given the mu the value of viscosity. So, mu equals to it is 1 poise or it is 1 by 10 Newton second per meter square. So, we will substitute it here 1 by 10 into 0.4 upon 0.15 into 10 dash 2 minus 3. So, it will be 266.66 Newton per meter square. Now, we need to calculate the force. So, we know we all know that f equals to shear stress or here tau into area area of the plate is given here. So, it will be 266.66 into the area is 1.5 meter square. So, it will be 1.5. So, the force required per unit area will be 400 Newton. Now, we need to calculate the power required to move this plate at a constant speed. So, we all know that force into velocity that is u here. So, force will be here 400 into velocity is 0.4. So, it will be 160 watt. So, the power equals to 160 watt and the force required to maintain the speed will be 400 Newton. These are the references. Thank you.