Unlike USB, power supplies with a DC barrel jack connector can have different polarities and voltages, making it far too easy to plug the wrong one in and possibly damage your device. To avoid this, let's decipher the printing on a DC adapter. First, there's voltage, 5, 9, or 12 volt are most common, whatever it is, it needs to match your device's required voltage. Then there's the current, which needs to be greater than or equal to what the device asks for, so a bit different than voltage. Lastly, there's the connector's polarity. 99% of devices require a center positive connector, which is usually denoted using this symbol. But watch out for center negative supplies, common in some audio devices. They use a very similar symbol, but you don't want to mix them up.


Good afternoon from the Kennedy Space Center in Florida. This is Space Shuttle Endeavour launch control. The countdown for launch of Space Shuttle Endeavour tonight on mission STS-89 is continuing on schedule. Launch is scheduled to occur at about 9.48 p.m. Eastern time and we are currently at a scheduled hold at T-minus three hours. Work at Launch Pad 39A as well as operations here in the firing room are continuing as planned. This is Endeavour's first mission to dock with Russia's space station mirror. The previous seven docking missions were all successfully done with the orbiter Atlantis. With an on-time launch docking of Endeavour with mirror is set to occur at about 3 p.m. Eastern time on Saturday, January 24th. And we're with live pictures now from the crew quarters and the operations checkout building as our seven astronauts are seated for their traditional meal prior to launch. Our Sharapov is a mission specialist as well as we just saw Mission Specialist James Riley here as Ivani Dumbar who is preparing for her fifth flight into space today. She is the most experienced astronaut of all the crew members today which are commanded by Terry Wilkett who will be leading this crew of seven. Andy Thomas will be remaining on mirror for four months. Michael Anderson and pilot Joe Edwards are preparing for their first flights into space today. Everybody looks like they're wide awake. They have been in fact awake since about nine o'clock this morning. They've had two meals since that time and this is simply a snack that they will have before they make final preparations to board the orbiter Endeavour and then launch tonight at our preferred launch time of 9.48 p.m. At the shuttle pad the final inspection team is continuing their operations to make final inspections of the orbiter as well as to look for any potential debris items that may be on the pad surface or on any of the number of walkways that go run up and down the full length of the vehicle. They'll also be looking for any build-ups of ice or frost on the external tank following the loading of the cryogenic reactants. And we have now moved to live TV of our astronauts that are being suited up. They have just completed their weather briefing and are making an effort to get a little bit ahead of schedule so they have moved on into the pseudo prune commander Terry Wilka of course being the commander of this mission is did again receive his weather briefing just moments ago and was told that we will proceed with our activities tonight that there are no technical issues that we're dealing with Bonnie Dunbar who was preparing to make her fifth flight into space tonight is also making final preparations to ensure that her suit is tight and snug. Joe Edwards of course seen he is the pilot of this crew and he is preparing for his first flight into space and we have seated here Michael Anderson again also making his first flight into space Jim Riley also making his first flight into space he is a designated mission specialist number one and he is saying hello to his friends and family who may be watching or who have actually come to the space center to watch his launch tonight Salzan Sharapov is a graduate from the Moscow State University. He was also a pilot instructor in the Russian Air Force and he was been training at the Gagarian Cosmonaut Training Center to be an astronaut or a cosmonaut candidate since 1990. Andy Thomas will be making his second trip aboard the shuttle but this will be his first time to visit the space station Mir which will be his home for the next four months. He will replace astronaut Dave Wolf who has been on Mir since September. Thomas is scheduled to be the seventh and final astronaut to live aboard Mir and at this time we do have live shots from the third floor of the operations and check out building as the crew exit their crew quarters and make their way down the hallway toward the elevator which will take them out to the astronaut van which will then take them out to the pad and they're being greeted by well-wishers and supporters employees at the Kennedy Space Center who like to get a last glimpse of the crew before they head off into space spending the next nine days in orbit five of those days docked with the Mir space station and the astronauts coming out of the quarters right now as they are being led by their commander Terry Wilkut followed by pilot Joe Edwards mission specialist Bonnie Dunbar Michael Anderson Salazon Sharpaugh James Riley and Andy Thomas and this is a view from the white room as our commander Terry Wilkut is making final preparations to enter the orbiter he is he will be the first to enter the vehicle so that he he can begin the enormous task of making sure that everything is set up and ready to go for a launch tonight mission specialist Andy Thomas making his second trip aboard the shuttle again he will remain on Mir for the next four months replacing astronaut Dave Wolf who has been on board Mir since September. Thomas will become the seventh and final astronaut to live aboard Mir pilot Joe Edwards has just now crawled into the orbiter and he will be followed by mission specialist Bonnie Dunbar the most experienced astronaut in this flight having gone into space four times already. Step five fifty four new tapes. Copy that's complete, check thirteen ninety. Thirteen ninety. And now it's at five fifty four? Five fifty four. OTC PLT, down check. PLT, this is OTC, I got you loud and clear, help me. Locked over by the computer. Evening Joe. CHD, CVSF, the CVSF sends to the air to ground one, verify active on air to ground one and monitor two three two for major count and verify loud and clear. CHD, ACD, verify loud and clear. CVSF, CVSF, verify loud and clear. And GVSF. GVSF, actually loud and clear. Loud and clear. Dave King is being introduced today as the new launch director at Kennedy Space Center. He is only the third launch director that Cape has had since we had returned to flight of the space shuttle. King began his career with NASA in 1983 as a main propulsion engineer. He later served as flow director for the Orbiter Discovery and as the acting deputy director of the installation operations director. And CDR launch director. Yes, CDR. K. Terry, looks like weather is good. Looks like we got a good vehicle and we're going to try to get you out of town tonight and be looking forward to seeing you back here in nine or ten days. Thanks a million.  And we have Orbiter Access Arm now being retracted away from the vehicle. This arm can be returned to position within seconds if need be. RTC PLT APU restart complete with three great dogmechs. Get out. RTC PLT APU starts complete with three good APUs. Thank you. And final error surface checks of the Orbiter's Alavons as well as the rudder are being completed at this time. This verifies the Orbiter's hydraulic systems. And the three main engines are being gimbled for a final test before launch. And we're standing by for the retraction of the gaseous oxygen vent hood away from the external tank and it is being retracted at this time. Inside the bronze color tank is about 500,000 gallons of super cold liquid fuels that run on the Orbiter's three main engines. Copy that. Flight crew, OTC. Closing launch divisors and initiate O2 flow. We begin 98 sending our last astronaut for his stay on mayor. We're going to howl for the Wolfman. That should work. We'll see you in a few days. T minus 13 seconds. 10, 9, 8, 7, 6. We have a dope start. 4, 3, 2, 1. We have booster ignition and liftoff of the Spatial Endeavour continuing the union of U.S. and Russian space endeavors. This endeavor will program. Houston is now controlling. The roll maneuver is complete. Endeavour is now in a heads down wings level position headed to a rendezvous with the mayor space station. I'm traveling at about 520 miles per hour. Endeavour's engines are now throttling down to 67% of rated thrust. Endeavour is now passing through the area of maximum aerodynamic pressure on the vehicle in the lower atmosphere down range from the Kennedy Space Center. 2.3 miles traveling at a speed of just about 870 miles per hour. Endeavour, Houston, go with throttle up.  One minute 19 seconds into the flight. Endeavour's three liquid fueled engines are now back at full throttle. 104% of rated thrust. Endeavour down range from the Kennedy Space Center a distance of about 10 and a half miles traveling at the speed of about 2,000 miles per hour. Just about seven minutes of powered flight remaining. Two minutes, nine seconds into the flight the booster officer confirms good separation of the solid rocket boosters. And never now down range from the Kennedy Space Center at a distance of about 38 miles. Endeavour, Houston, performance nominal. What's nominal? Endeavour, Houston, two engine towel. Two engine towel. Two minutes, 35 seconds into the flight. Endeavour's performance has been as expected and in the event of a single engine failure. Endeavour could now reach the transatlantic landing site at Zaragoza, Spain. Telemetry still continuing to indicate that all three main engines and auxiliary power units and fuel cells are performing well.


Hi and welcome to our session. I'm Kanika and I'm going to help you to solve the following question. The question says find the length of the meteons of the triangle with vertices a having coordinate 0 0 6, b is having coordinate 0 4 0 and c is having coordinate 6 0 0. Before solving this question we should know that if p having coordinates x 1 y 1 z 1 and q having coordinates x 2 y 2 z 2 are two points then the coordinates of the middle point of the segment p q will be x 1 plus x 2 by 2 y 1 plus y 2 by 2 z 1 plus z 2 by 2. You should also know that distance between points p and q that is p q is given by square root of x 2 minus x 1 whole square plus y 2 minus y 1 whole square plus z 2 minus z 1 whole square. The knowledge of this is the key idea in this question. Let's now begin with the solution. We are given that a b and c are three vertices of a triangle a b c. We have to find the length of the medians of this triangle. Let d be the middle point of the line segment joining points v having coordinates 0 4 0 and c having coordinates 6 0 0. Now the coordinates of t, coordinates of v will be 0 plus 6 by 2 4 plus 0 by 2 0 plus 0 by 2. This means coordinates of dr 3 2 0. Now we will find length of medial ad 0 6 and coordinates of dr 3 2 0. Now using distance formula we will find ad. Now here x 1 is equal to 0, y 1 is equal to 0, z 1 is equal to 6, x 2 is equal to 3, y 2 is equal to 2 and z 2 is equal to 0. So ad is equal to 3 minus 0 whole square plus 2 minus 0 whole square plus 0 minus 6 whole square. This is equal to square root of 9 plus 4 plus 36 and this is equal to square root of 49. And this is equal to 7 units. So distance between a and d is 7 units. Now we will find length of medial v e. Let e be the middle point of the segment joining length a having coordinates 0 0 6 and c having coordinates 6 0 0. Now we will find coordinates of e. Now coordinates of e will be 0 plus 6 by 2 0 plus 0 by 2 6 plus 0 by 2. So coordinates of e are 3 0 3. Now we will find length of medial v e, coordinates of v are 0 4 0 and coordinates of e are 3 0 3. Now using distance formula v e is equal to square root of 3 minus 0 whole square plus 0 minus 4 whole square plus 3 minus 0 whole square and this is equal to square root of 9 plus 16 plus 9. This is equal to square root of 34. So length of medial v e is square root of 34. Now let the middle point of the segment joining points a having coordinates 0 0 6 v having coordinates 0 4 0. Now coordinates of f will be 0 plus 0 by 2 0 plus 4 by 2 6 plus 0 by 2. So we have found out that coordinates of f are 0. We will find length of medial coordinates of c are 6 0 0 and coordinates of f are 0 2 3. So c f is equal to square root of 0 minus 6 whole square plus 2 minus 0 whole square plus 3 minus 0 whole square and this is equal to square root of 36 plus 4 plus 9 and this is equal to square root of 49 and this is equal to 7 units. So required lengths of the medians are 7 square root of 34 and 7. This is our required answer. So this completes the session. Bye and take care.


Welcome back. It's still the breakfast and plus TV Africa like I said before the breaker We're looking at them psycho social issues affecting us as a people and in recent times We have been played with reports of domestic violence sexual based violence And of course, you know sex tapes, you know about children and all of that where we actually had it for best right now We'll just stay on domestic violence and we want to know we're asking questions Just how far can the church religious leaders, you know go when it comes to the issue of domestic violence? Remember what happened with the case of popular gospel singer Osina Chinwachuku how she was allegedly allegedly beaten by Her husband and eventually she died although the the the case is still being investigated But this time around we have the can chairman in Keduna State joining us Reverend John Joseph Hyab many thanks for joining us on the breakfast on plus TV Africa Thank you for having good morning. Hello. Thank you. All right. I'll just dive straight into it right now What's your what's the church's position when it comes to domestic violence? Most times are when issues like these happen and Churches or religious leaders would actually say that the woman cannot live the husband because The Bible that's what they usually quote for us that the Bible or the church does not support the voices and all of that But what's the position of the church when it comes to domestic violence? Yes When the Bible equally does not support evil wickedness brutality and any form of violence So just as the Bible do not support diverse the Bible to do not support evil and wickedness I'll try to explain this to many people When Jesus was speaking to his disciples and responded to a question That on what reason should a man divorce his wife and the reason that we're given was that on Marital on faithfulness I think we need to look into scripture and understand what is the definition of Marital on faithfulness Because the Bible in first Timothy chapter five a state says that we ever do not care To take care of his family or to protect his family or to provide the need of his family It was that an infidel and the same scripture says that you should have no equal you would be unbelievers with infidels So if someone beats his wife battered his wife wants to kill his wife is an infidel So how many call you up with an infidel is also contradicting the scripture so we have to apply it based on what the scripture says not just an isolated verse because I Cannot as a father give out my daughter and a man that claims to love my daughter now change He loved me my daughter and become evil beating her and want to kill her and I say no no no because we go to church No, no because the Bible it's a Bible tells me that I should have no equal yok We don't know believer with an infidel because by his action he has shown that he do not know God He do not serve God. He is he does not fear God when you look at the Bible in faith Peter chapter 3 7 the Bible specifically said that men should treat their wives with respect Understand them that they have equal they are weaker vessels Because the kind of treatment you treat your wife could determine whether your prayers will be answered So if a man has really willingly decide that he does not want his prayer to be answered That means the man is out of faith. So the Bible condemns between Violence against women or violence against any human being and we ever indulge in that has identified himself as an infidel And so she'll be she'll not be treated as the brother And so keeping a wife under such a present is not Bible card and neither are you helping her spiritual? Okay, so now let's come to Let's also look at the fact that what can the body of Christ now on the church do as a role in Showing that domestic violence is prevented. Of course, not everyone Has the understanding of the scriptures that you have put out and not everyone would actually, you know Understand that scripture in different denominations across the country So constantly you find out that victims of domestic violence, whether it's a man or woman They don't want to talk about it. They constantly stay in the marriage because For the fact that God hates divorce and that's the scripture that's predominant in their minds And so they stay and some of them get killed in the course of all of this So what can the church do in this fight against domestic violence? Well, before I answer that question, let me add here that when we talk about scripture We don't talk about denomination the Bible is not a denomination. The Bible is the infallible word of God and Pastors must leave and teach the Bible not teach denomination I think as I agree with you one of the reason why we are where we are today is We try to apply the Bible on the basis of denomination denomination not on one God's Because you have to look at the Bible holistically it has no Catholic it has no Pentecostal It has no protestant It has only the word of God and people must live in accordance with the word of God When people don't go in accordance with the word of God I want to go by church Then we'll be doing something evil and when you appear before God God wouldn't ask you as a woman who was a battered and killed that don't welcome you are a faithful member of Equal you are a faithful member of baptism or redeem God is going to ask you whether you know him Honestly, let me come to your question the church has so many roles. The church is actually an institution where grooms trade and Christians Among many of the things that the church needs to do is not one the church needs to intesify Teaching you see there's nothing But the church seems not to be doing a lot about teaching what the church does mostly is only on weddings day Unwilling day that the pastor will preach about marriage about loving your wife and after that you find meaning of the Actually giving both seminar on that anymore Even the marriage counseling that we used to go sometimes we think that there are certain place that we don't want to talk about It is the taboo. We must be open to intending couples for them to understand what it means to love what it means to care What it means to defend one another?  The church have many reasons they discipline people. The discipline should not be restricted to those other ones The discipline should also come on this and not only that the church must show Example, do you know that even some pastors would preach the quote by guilty of even what we're talking about So if we don't lead by example The chances is that people wouldn't learn anything if you want to see the law You should be alive people watch our wives when we come to church on Sundays They see how their wife their faces are shining they are not smiling and they begin to suspect is everything all right Is there a problem in the house? So we have to show that good example So when the church teach correct review and example, we may overcome them. All right, Reverend I'm high up. Let's talk more about them the role of the church and the place of the church because often time most people don't talk about these things and most people just are silent about it because of Stigmatization and Sometimes the church might some churches, you know might give them the back door or the back seat over time You know, for instance, you are actively involved in the church's choir You are like a role model and the like what? What kind of modeling will you be given to the other to other people or the members of the choir or the church if you're not divorced or if you Involved in issues of I'm domestic but most times I do ask you to go home and pray about it And that even if you are divorced some churches would actually ask you to take the back seat because you are not Leaving by good example. So how do we even strike a balance? How do we know where to draw the line really? You see our job as a church is to help those who come to Russia Is to let them go beyond where they came when they are when they came to our church If we do that We'll be able to help them out But you see it is dangerous when you want to have a weak person and you are hiding this weakness It is dangerous when you want to have a man who is sitting and you want to provide the same It is dangerous when you want to have a man or a person who is in danger But you want to make the danger look as if he's here I think this is where many churches get it wrong There is need for us to openly speak about this to openly correct this to openly discipline those who do this To openly review those who do this without covering it Then the man knows that this practice is not and the woman knows that this practice is not acceptable in our church But even as we do that we are not in any way trying to contain them There are practices there are attitudes that the church will not tolerate the church will not talk for you So these are the ways we will have people to come but as you rightly said Maybe church is finding difficult to speak about this and sometimes those who do this act of violence against other women or men Powerful people in the church probably be givers of the highest helping and so everybody is afraid to tell to correct them To rebuild them and do the attention to do things they are doing That is where pastor and ministry is come to test as a pastor Your job is to show the person who is wrong Brother what you are doing is wrong and it's not a good testimony for our church. So we cannot allow It's not just about putting him in the back seat. You see the back seat is also a tradition somewhere But there are certain ways you and church members will know this thing is wrong today Actually everywhere we are discussing this but allow us a week or two once we are we overcome this story We forget it and will not mention it again until another one's up. This is what we supposed to be teaching every day We supposed to be reminding our members look We're supposed to even begin to guide the teenagers the teenagers must begin to see the fellow woman But the young girl by their side in class the young girl in the teenager church as their friend as part of them You see children grow up to think that any other person that is not like them They are the above the other person or this you show the other person They are much women and that's how they grew Growing to be the uncles and grown to be their wife Oh, they learn to see their parents beating their mothers and they think that beating the woman makes you a big man So we need to do this beyond just Putting people in the back seat take it to the children show the example bring them together with the parents Open up the competition in church Women cannot speak of people are not talking just because we've not given them opportunity to voice out when we give them opportunity to voice out That would be probably let me put in this way That's one of the challenge we have with having a mega assembly where you have people in thousand You don't even know where they go from you don't know where they what they do But in church we got some people supposed to have units where there are representative votes For people But today people are scrambling to have a food show Where they will say I am one of the big pastors in town And you don't even care what happens to the people's life and they keep doing evil until something like this happen All right, thank you so much Reverend hire, but I just want to quickly put in one question I want you to just answer me in a sentence if a woman who has been battered who is in a Abusive relationship comes to you as a pastor and complains about him what the husband is doing to her What would you advise her to do? Well, it's only being on the history of the battery and how long they've been together whether they start learning lessons of life But if it's an habitual person who has been battered is why if I'm a pastor I would ask her to prayerfully consider whether she wants to remain alive and serve God Or she wants to die and claim to be sad All right. Thank you so much Reverend Joseph high up would do appreciate your time and all the thought you have shared with Nigerians this morning All right, Reverend Joseph. Yeah, I'm high up is I'm the chin can chairman in Keduna state mercy You have heard him or he said that I actually could take out of all of that is that this Conversation should be continuous because this is like in the front burner like after one or two weeks now people You know tend to not talk about it anymore until all that new issues come up They said it should be a continuous and ongoing process Yes, and the church needs to understand but like he's right dimension So you have a thing of denomination and you have the fact that the scripture has been you know Interpreted in different Misinterpreted and people constantly give different interpretations so with people would read the scripture independently of the previous Verses that you have and that has also constituted a problem. Whatever the Bible says is what it is You don't need to look for a dictionary to interpret it. It's that simple But if on me what is most worrying is the fact that what happens? How do people move from being very sweet to be very bitter to a point where you're taking a machete? And then you're trying to stab another person and kill them and see you know take joy in inflicting pains on the other Partner, I'm just wondering how did people just switch, you know from this side how we lost our humanity Well, that's the size of the show for today Thank you so much for sitting by to watch us and of course, you know You can actually contribute on our social media platforms messy And that's it on Facebook Twitter and Instagram You do can also subscribe to a YouTube channels of plus TV Africa and plus TV Africa lifestyle many Thanks for watching. I am messy book will have a great day, and I'm Justin I'll continue standby for the news coming up momentarily


I would like to talk something about two exercises in that is 13 and 18 because when it comes to students these need to be explained properly. So, OS 13 is about the situation where we have a throttling calorimeter and the situation is measure the state of wet steam that is mixture of water and steam x less than 1. So, here we know that the phase rule dictates that pressure and temperature are not independent of each other. So, we have to have one of them at most and something else. So, how do you determine the something else? It is difficult to do density measurement or it is difficult to do energy measurement. So, under certain conditions we use something called a throttling calorimeter. OS 22 is an illustration of throttling and separating calorimeter. So, you can extend this idea in OS 22. Here the idea is like this. Because the situation suppose you have a duct through which steam flows and you measure its pressure say P1 and temperature T1 and you find that the pressure and temperature turn out to be lie exactly on the saturation line. For example, the pressure could be if you look up the steam tables pressure could be 2 bar and temperature turns out to be 120.2 degree C or pressure turns out to be 5 bar temperature turns out to be 151.9 degree C. Such situations typically occur at the exit of a boiler steam generator just before it goes to the super heater or some equipment which follows the boiler drum. But we want to know what is the state is and with such a situation the state could be anywhere from saturated liquid to dry saturated steam. The throttling calorimeter is a device by which we can determine the drainage fraction of steam under the following conditions. Number one, the pressure is higher than ambient. So, that if we take a sample of steam from this pipe and connect the other end of the sampling device to air steam will start automatically flowing through it. We will have not have to use a vacuum pump for anything. And second this works when the drainage fraction of steam is very near one within a few percent of 100 percent. It may not work when the drainage fraction is as low as 0.8 or 0.7, but it is likely to work when the drainage fraction is something like 0.949596 and so on. So what we do is the following. We take a sample out of this, maybe we put a tube with some holes and some steam a representative sample is taken out. Now it is expected that P1 is greater than P ambient. So, if this is connected on the other side to the environment steam will start flowing through this and maybe a large amount of steam will flow. What we do since we want only a sample we put here what is known as a throttle valve. A valve which is only partially open or sometimes a small orifice or a series of orifices. The job of this throttle valve is to provide enough flow resistance so that even with the large pressure difference between P1 and ambient only a small amount of steam flows through this. Now as it reduces in pressure the volume increases so we provide a large area for the steam to flow out. So the inlet is here and we consider our open system to be made up of from the inlet to the sampling tube to the exit and at the exit we measure the pressure P2 which is expected to be P ambient and we measure the temperature T2. So this is the inlet state I state 1 the exit state E state 2 and there is a small amount of m dot which flows through this. The whole thing is well insulated it is not a very large piece of equipment. So we expect that it runs in a steady state there is no power output or power transfer it is well insulated and because it is a small equipment data EP is negligibly small and because of the small sample which is extracted and the large area which is provided at the exit it is expected that data E or K is also negligibly small. If you start with the steady state energy equation we get Q dot minus W dot S is m dot HE minus HI which is H2 minus H1 here plus delta EK plus delta EP. Now here Q dot is 0, W dot is 0 these two are expected to be negligible. So we end up with the result that H2 equals H1 that means from the inlet state to the exit state or for the inlet state and the exit state what we have is the same enthalpy. And if you now look at the properties of steam if you take it on say the PV diagram let us say let this be the initial pressure P1 inlet pressure and let this be the inlet state slightly wet. This is the saturated liquid line this is the dry saturated vapor line and let this state be the inlet state. If you look up our enthalpy values you will find that if I keep the enthalpy the same and if I reduce it to a lower pressure this line is likely to go like this and you will end up with a state 2 which is at pressure P2 but which is likely to be superheated. And now if you are in the superheated zone here P2 and T2 decide the state. So from here we obtain H2 and since one is wet steam P1 and T1 is not a good pair. So we use P1 and then we use H1 which from this relation turns out to be H2. If you proceed with the details of this problem you will find that in this particular case P1 is 10 bar state of steam after throttling is 0.75 bar. So they have used the vacuum pump for some such device to reduce the ambient pressure near the exit of the throttling calorimeter to 0.75 bar and T2 is 100 degree C. Now from this 70.75 bar and 100 degree C if you go into our steam table you will find that 75 degree C is 75 bar and 100 degree C is 0.75 bar and C is tabulated on page 11 roughly slightly above the middle 100 degree C and 0.75 bar and here H2 turns out to be 2679.4 kilojoules per kilogram and hence H1 is also 2679.4 kilojoule per kilogram. Since P1 is already given to us as 10 bar, 10 bar and H1 of 2679.4 kilojoules per kilogram decides the state and now we go to table 3 sorry table 2 page 8 where we notice the 10 bar line and if you notice that at 10 bar HF that is HF at 2 is 762.8 kilojoule per kilogram Hg at 2 is 2778.1 kilojoule per kilogram. And then you say HF2 is less than H1 is less than Hg2.  So while explaining I have solved almost all the full problem for you. Now another problem which I want to talk about is OS 18 OS 17 and OS 18 both per kilogram are attained to what we call a heat exchanger. Now we have to tell our students because when they learn this they have not studied heat transfer. So they do not know what a heat exchanger is. If you take them on a round of your campus then you can show them heat exchangers of some times which you will find in your central air conditioning plant or chiller plant and things like that or even open the bonnet of an old car. New car can also be used but the equipment is so compactly arranged and so cluttered in it that it is difficult to show the various subsystems. If you show them an old car you can show them a radiator and explain that it is a heat exchanger but in a thermodynamics class all that you tell them is that heat exchanger is a open thermodynamic system. So if this is a heat exchanger there will be two streams flowing through it without mixing with each other. So this is the transfer type of heat exchanger. Say fluid 1 rate m dot 1 enters at state 1 i and leaves at state 1 e. Fluid 2 m dot 2 enters at state 2 i and then the fluid 2 m dot 2 enters at state 2 i and leaves at state 2 e. Tell them that look this is only a schematic it is not necessary that the two fluids flow through two channels just next to each other as parallel lanes on a highway. They could cross each other one tube could be rolled on to the other they could be across each other they could be against each other. There are types of arrangements very complex once in real life and but what we should know is there are two streams not mixing with each other. So what goes in at 1 i must come out at 1 e and what goes in at 2 i goes out at 2 e. So this is an open system two inlet two exit no mixing it works in a steady state and although we claim it to be a heat exchanger overall it is an adiabatic system it is usually well insulated and no attempt is made to extract any power. So apart from q equal to 0 w dot s equals 0. Also the change in kinetic energy for any stream is negligible change in potential energy for any stream is also negligible. Now if you look at our equation the steady state equation is q dot minus w dot equal to you will have m dot 1 h 1 exit minus h 1 inlet for one stream plus m dot 2 h 2 exit minus h 2 inlet. This will what will be the reduced form of the first law but we should derive it by the general form. On the left hand side w dot is 0 w dot s is 0 q dot s is also negligible so you end up with this expression to be equal to 0 that is the heat exchanger equation. What happens inside the heat inside the heat exchanger is there is an exchange of energy in the form of heat between the two fluids and because of that as you notice here since m dot 1 and m dot 2 are both positive the flow rates one enthalpy difference will be positive one enthalpy difference will be negative depending on which it said to be the hotter fluid and which it said to be the colder fluid or cooler fluid. Here we have to determine for example in OS 18 we are given 120 kg per hour of saturated water at 8 bar enters a heat exchanger and leaves at 4 bar 200 degree c. So in OS 18 stream 1 is water, 1 inlet is saturated water at 8 bar, 1 exit is the heat exchanger 4 bar 200 degree c. So there is a in the other side the other stream is hot air enters at 600 degree c, 600 degree c 2 bar and leaves at 240 degree c 2 bar, 2 inlet is 2 bar 600 degree c and 2 exit is 2 bar. So how do you pressure difference on the air side? 240 degree c. So now you will notice that you can determine h i h e for stream 1, you can determine h i h e for stream 2, m dot 1 is given 120 kg per hour. So from this equation the only unknown remains to be calculated is m dot 2 which you can now calculate. Heat transfer rate from air to water remember here our system is the complete system, but you can devise another control volume and that control volume is containing only the one side through which say air flows. And if you want you can have another control volume, control volume 1 is that part through which only the steam flows and you will have this q dot from 2 to 1 the rate of heat flow. Remember if we consider the whole heat exchanger as our system any internal heat transfer will not be computable. So to determine the heat transfer rate from air to water we will have to put a boundary between air and water. So we will consider either a green control volume which is the water flow control volume or the red control volume which is the air flow control volume. And then when you apply your first law to this say to the water side you will get q dot 2 to 1 equals m dot into h 1 e into h 1 i in which you can from which you can calculate q dot. The entropy production rate can also be calculated we have the expression just sum it up over 2 streams and b and you can proceed from there. I think other exercises you can tackle yourself 1 1 0 0 m e s pillai nu panvel. Sir we are talking about second law about energy you have not made any comment on that. There is various ways in which the laws of thermodynamics particularly the second law can be interpreted. I have left it at entropy differences I have left it at the inequality which comes out of the second law. The maximum I have done is defined entropy production and says any process which takes place is one in which entropy production is positive. At most it could be 0 in which case it will be a limiting ideal reversible process. People interpret it as degradation of energy but without defining what is meant by degradation of energy. People interpret it as increase in randomness increase in chaotic behavior and things like that but we do not have to interpret it anything like that it is good enough for us to interpret it as a change in entropy of adiabatic systems being always positive in real situations. That is it over to you. Thank you very much. Over and out. 1 1 1 3 s b patil in the poor. Sir my question is how to derive the reducer equation of state for under wall gas. How to derive the reduced equation of state? In fluid mechanics we are used to using dimensionless numbers. For example velocity can be made dimensionless by dividing it by either the free stream velocity or the mean velocity in the duct. We have Reynolds number and all that. So in thermodynamics when we compare different fluids and see whether their characteristics are similar we tend to use what are known as reduced variables. So instead of pressure we define pressure divided by some reference pressure, temperature divided by some reference temperature and volume divided by some reference volume. For fluids which have a critical point and which is true for most of the fluids the critical state pressure, temperature and volume at the critical state is used as the reference state. So all that you do for deriving the reduced form of the van der Waals equation is write pressure as critical pressure into reduced pressure P r, temperature as critical temperature and to reduce temperature T r and the specific volume as critical specific volume V c multiplied by reduce specific volume V r. Now that way you will end up with an equation which contains the parameters a, b and r as well as the critical constants V c, T c and P c. We have already derived relations for P c, V c and T c in terms of a, b and r. If you use those relations you will notice that a, b and r get eliminated and the equation remains only in terms of P c, V c and T c. That is the reduced equation of state or reduced form of the equation of state. The advantage is once this happens once you are able to get the reduced form of equation without any P c without any a, b or r in it then in principle you can use it for any van der Waals gas or any gas which obeys the van der Waals equation of state. Over to you. What is the significance of calculation of entropy in steam generation process? Calculation of entropy in steam generation process. I do not know, calculation of entropy and entropy differences is significant and good to look at in any process for that matter. Nothing special about steam generator process. Actually it is the entropy comes into its own and it is very important when we have adiabatic systems when like turbines, compressors, nozzles, sometimes even heat exchangers. Of course steam generator is a heat exchanger but we have a high temperature source from combustion. So there is significant amount of heat transfer, significant temperature difference also. So there will be significant entropy production as we have defined that term. Apart from that in the design of boilers the entropy generation or anything is not used. I know that. Over to you. Thank you sir. Over and out. 1272, Mangala Yatthen University, Beshwautar Pradesh. Sir, yesterday we have described one formula TDS equal to DU plus PDV. And I want to ask whether it is valid for flow system or open system or all the systems. See TDS, this is a basic property relation. It is not for any process or anything. So as a relation between properties of fluids you can always use it. It has nothing to do with whether it is an open system or closed system. Now if we are at it, I would like you to you and all others who are listening to understand and appreciate this because this quite often leads to some confusion. Now consider for simplicity a closed system and a small process. Now in that small process we will have DQ equals DE plus DW. Now let us assume that DE equals DU and let us assume that it is a simple compressible process. Now in that case I can write DQ, now remember this is first law. DQ equals DU, now simple compressible system I can write this PDV plus DW other where DW other is other type of work say electrical or stirring or any other non 2W type of work. The only two way work is PDV because it is a simple compressible system. Now this also is first law. Now what does the second law say? The second law says that DS is greater than or equal to DQ by T. Since T is always positive I can write DQ is less than or equal to TDS. Now that means I have combined this and this and I will get TDS is greater than or equal to DQ and DQ is DU plus PDV plus DW other. Now for this equation I have used first law and I have used first law. Now remember this equation I will write it again on the top of the page TDS is greater than or equal to, TDS is greater than or equal to DU plus PDV plus DW other and this is a consequence of first and second laws. Now I will use the property relation. Now which we have derived yesterday the property relation says TDS equals DU plus PDV and why can I use this because this is a property relation for a simple compressible system. So, now I have one equation which is an inequality for TDS after first and second law and another equation which is an equality for TDS using the property relation. Now the next thing which I have to do is replace in this equation for TDS DU plus PDV and what do I get? I get DU plus PDV is greater than or equal to DU plus PDV plus DW other and now DU plus PDV will cancel out from either side and I will get for a simple compressible system DW other is less than or equal to 0 for a and what does it mean? That means if you have a fluid system like a liquid or a vapor or whatever then if you do work for a simple compressible try to do work by a mode other than the PDV mode because this is DW other that work interaction will always be such that you can do work on the system you cannot extract work from the system and this is the thermodynamic consistent demonstration of the fact that you can put a stirrer in a fluid and start stirring it doing work on the system, but you cannot put a stirrer in a fluid which is already in equilibrium and ask the fluid stir the stirrer and do work on it. It cannot do that because the laws of thermodynamics prevented this is what we have shown. So this is another justification that work interactions which do not depend on any property of the material will be one way work interactions and this is the one way direction that is demonstrated by the laws of thermodynamics over to you. Okay, thank you sir over to you sir. Chikodi 1089 KLE college of engineering and technology over to you. Actually we want to know that how that a plug flow has been characterized yourself. Now the energy of the exit plug will be equal to the mass in that that is mass in that much volume multiplied it by its specific energy. The specific energy for the inlet plug is EI the specific energy for the exit plug is EE and if you go back a bit you will see that the mass in the inlet plug is rho I AI VI delta T the mass in the exit plug is rho EE VI delta T. So all that has been done is we have taken these two expressions and use those mass in the inlet plug and exit plug whatever you see in the brackets here is mass in the inlet plug what you see in the brackets here is mass in the exit plug and all that we have done is multiplied the mass in the inlet plug with the specific energy at inlet mass in the exit plug with specific energy at the exit over to you. As we know that two temperatures were taken for the heat engine is there any concept of how the temperature distribution effect can be considered for the efficiency calculations. The crucial thing here is to realize that it is the corollary of Carnot which is more important that if you have two temperature levels then any reversible heat engine will have the same efficiency. The beauty of this is this does not depend on any detail of how that reversible engine works. So it has absolutely no relation with the temperature distribution from T1 to T2 which may be occurring inside the engine. We just do not have to worry about it and that is the strength of Carnot theorem and it is only on that strength that we can define a thermodynamic scale of temperature over to you. If the water is heated in infinite number of stages by bringing the water in contact with infinite number of reservoirs each succeeding reservoir being at a higher temperature than the next receding one what will be the change in entropy of the universe. This is I think an exercise either in Sears book or the Zimansky book. You can show that as you increase the number of reservoirs each increasing by smaller and smaller delta T the you can show that the change in entropy of the universe reduces from a large positive number it will come to a small positive number but for it to reach 0 you will have to make the number of reservoirs really to infinite. Any finite number will have a small but finite entropy production making the process irreversible but your idea is right that is what we will need but you will need an infinitely large number of reservoirs even reservoirs differing by 1 degree centigrade will not do 0.1 degree centigrade will not do you say 10 raise to minus 9 degree centigrade even that will not do because that is still a positive temperature difference over to you. Why we ignore the pressure variation with elevation for a storage tank in a gas the if the density of the gas is not very large then compared to the mean pressure the pressure variation will be small and since the pressure variation is small the variation in other properties also like is also likely to be small. So the results which you obtain regarding what happens to the gas and the way it behaves will not significantly differ if you replace that varying pressure by a mean pressure at an appropriate value. The purpose of doing all these approximations is not to say that that does not matter but to say that the variation may be of some consequence but if I neglect that and base all my calculations on the mean pressure the results which I obtain are good enough to do all the things which are needed to be done for example the gas drain rate or the gas heating rate or whatever but there will be situations where perhaps you will have to consider that variation in which case there is no choice you cannot neglect that over to you yes. Is it possible to attain to zero temperature zero Kelvin temperature experimentally. No because if you attain and create a system at zero Kelvin then that means you can run a reversible 2 T heat engine between some other temperature say ambient and zero Kelvin and that will have an efficiency of 100 percent so that itself will violate the Kelvin Planck statement. So zero Kelvin is a temperature which we can write down on paper we can discuss it in a workshop like this but which will not be attained. Can we call that entropy will measure the irreversibility. Not entropy, entropy produced or entropy production is a measure of irreversibility and next week when we considered combined first and second laws we will be studying what is traditionally called exergy analysis or availability analysis where we will provide some significance to the quantitative or the numerical value of entropy production. Today we can only say that any real process is one in which the entropy production has to be positive in the limit it can be zero but that would be an ideal reversible process and we are unlikely to be able to execute such a process in practice. But what is the difference between a process in which the entropy production is say 1 kilo joule per Kelvin and another in which it is say 2 kilo joules per Kelvin that we will be able to realize only after studying the combined first and second laws next Wednesday. Over to you. Thank you sir, over and on. 1150, Godavath institution's Atigre over to you. Sir my question is what is the value of drainage fraction at critical point. Okay see drainage fraction is defined only when there is a distinction between the liquid phase and the vapor phase so that density of liquid and density of vapor have two distinct values and so are other properties. At the critical point there is no distinction between the liquid phase and the vapor phase that is the lowest pressure at which it occurs. Since there is no distinction in the liquid phase and vapor phase there is no meaning in defining a drainage fraction at the critical point over to you. Sir can you measure the entropy? By measure you mean a direct measurement of entropy then the answer is no entropy or entropy difference between two states can always be derived but cannot be measured. Similarly even energy difference between two states can always be derived but it cannot be directly measured. Sir as we are having static sign dynamics in engineering mechanics like that is there the study like thermostatics as we are saying thermostatic valve and what about thermostatics sir the study of engineering branch is there. Okay actually since we have we lay significant emphasis on equilibrium may be things pertaining to equilibrium states that is property relations etc. you could consider as thermostatics in our course where a change of state relation between processes interactions and end states that can be considered thermodynamics and if you want to bring it the time rate by considering some other extraneous properties like conductivity and all that in that case perhaps the science of heat transfer which we will be studying or students will be studying slightly later that also could be included in so called thermodynamics over to you. Sir yesterday it was a discussion can we says the opposite word of sublimation as the throttling because during grain we will get the ice blocks and that is the instantaneous process and also in a jet plane where air particles are connoted directly into the ice particles is it so with this opposite word of sublimation is throttling is it right sir. No throttling is an entirely different phenomena throttling is a simple fluid dynamical process in which in a small zone like a capillary tube or a small orifice or a slightly opened valve the resistance to flow is so large that even a small amount of flow requires a large amount of pressure drop that is all throttling the effect of throttling is to be calculated thermodynamically as we have done in one of those exercises and you will realize that it has nothing to do with the sublimation process in solid state physics and in material science sublimation has an opposite but they use the same word condensation. So they say that carbon dioxide vapor condenses directly into solid carbon dioxide. So technically the word condensation can be used to denote a liquid of a vapor as well as the solid of a vapor whereas a liquid becomes solid it is called freezing gas becoming liquid is known as condensation in a similar fashion gas becoming solid is also known as condensation over to you. Okay sir when we are defining the temperature in the textbook we will see the meaning it is a degree of hotness or coldness but when we are defining to the electronic level for example when we are defining the current we are saying that charge transfer from one electron to another electron then how we can define this temperature with respect to the atom level considering the electronics and the kinetic energy like that sir. Okay in our scheme of thermodynamics temperature was only the a label given to isotherm labels given to various isotherms were defined as temperature we later on quantified it using the second law of thermodynamics Carnot theorem etc. etc. If you want to give a different interpretation to temperature you will have to go through kinetic theory where kinetic theory derives relations where for a conglomeration of particles which we in the continuum domain say behave like a gas you can derive an equation of state where you can show that the volume multiplied by the mean momentum of the particles equals some constant into the mean kinetic energy of the particle okay and then we compare this with the our equation of state from macroscopic thermodynamics and say that look this is very similar to pv equals RT provided we assume that p represents the average momentum of particles and t represents the average kinetic energy of the particles. So that is one way you can interpret temperature as kinetic energy of particle actually even kinetic theory does not really say that temperature is the mean kinetic energy of particles you can say temperature can be used to represent the kinetic energy of particles that means for a given set of particles if they are in a state where they have a higher kinetic energy they will have a higher temperature if measured on the macroscopic scales and vice versa over to you. Sir while we are considering the plasma state of steam or water is it the ideal state we can can we say that plasma state of water is the ideal state. No there is see there is no such no state as an ideal state an ideal thing is something for us to define ideal gas we call it an ideal gas because we want to call it an ideal gas the gas does not itself know that it is ideal or otherwise and for a fluid like water there is no such thing as an ideal state we can only have a reference state that is it and even the reference state is for us to define over to you. Sir for the turbine and the compressor e raise it is decreasing and increasing we are finding out the efficiency now you are giving the example of the duct how you derived the efficiency for the duct. No there is no such thing as an efficiency for the duct the idea of isentropic efficiency is only for three components a nozzle a turbine and a compressor that is it for no other thing something like an isentropic efficiency is defined and remember that that isentropic efficiency it is something which we define thermodynamics ends by telling you that entropy for such an adiabatic system should be such entropy change will be such that at the exit it will be higher than that at the inlet except in the limiting case in which case it will be equal that is where thermodynamic after that it is for us to define using those ideas over to you. Thank you very much center 1001 MA90 Bhopal over to you. Sir yesterday you are discussing the property relations yes in that you are discussing L-Mode function and Gibbs function right so first thing what is the significance of these two functions and second one is can you give some examples in the real life where we find these actually functions. Okay the utility of these functions is mainly from the point of view of thermodynamics and particularly of physical chemistry they have been defined because they have been found useful the simplest example of this is enthalpy has been defined because it has been found useful and we have that u plus pv term coming up quite often particularly when we have open thermodynamic system actually there is nothing wrong if the whole world decides to forget about enthalpy and works only about only with u and pv but then every time we will have to we will not tabulate enthalpy but we will have to work with u and pv in a similar fashion the two functions Helmholtz function A and Gibbs function G have been derived because they have been found useful in doing detailed thermodynamic calculations and calculations in physical chemistry. We are not spending much time on property relations in fact given to given the choice I would spend another 5 to 6 hours with my students on property relations demonstrating to them what is the utility of A all for a hint in property relation exercises yes the last two exercises PR 20 and PR 21 we look if you look up PR 20 it asks you to demonstrate that if the Helmholtz function or specific Helmholtz function of a system is specified as a function of temperature and volume then all properties including any change of phase saturation lines can be derived and in fact this is the way our steam tables are specified if you go to the link provided on the Moodle page through the NIST steam tables you will find that the specification of properties of steam is only in terms of one single function A as a function of T and V from there everything else is defined or derived including critical point liquid vapour saturation point from triple point onwards everything else including specific it can be extracted out of it that is the power of the Helmholtz function but in our day to day calculations we do not come across that so often Gibbs function is useful because we have showed yesterday that the work which we can extract from a system which executes a process which is isobaric come isothermal would be limited or the maximum work which can extract will be the decrease in the Gibbs function. So this is the this is related to the chemical potential of a reacting mixture in fact if you study physical chemistry you will soon be made to realize that chemical potential is nothing but specific Gibbs function with respect to the change in one particular component what is known as the partial molar Gibbs function that is the chemical potential. So chemical equilibria rates of reaction all those things they depend on Gibbs function since we are not delving any deep into combustion and chemical reactions we will not be appreciating the importance of Gibbs function in this series of lecture. However it is my duty to expose you that there is something called Gibbs function which we should be aware of over to you. Type is the parameter in steady flow energy equation like q dot term is joule per second then how thermodynamics differs from subject heat transfer. See here you will notice that this first law of thermodynamics is derived just by differentiating the first law with time q dot it is still related only to energy changes or energy change rates and work rates it is not related to any temperature difference or temperature gradient it is the job of the science of heat transfer to relate the difference in temperatures to the rate at which heat is transferred. For example yesterday we solved a problem I think the very first exercise is in the second law it says there is a 150 watt of steady heat flow from one system to another thermodynamics does not tell you how that 150 watt is arranged that is the job of heat transfer over to you. Can you tell me the difference between ideal gases and perfect gases too? I do not really know because when I was in school the idea of ideal gas and the idea of perfect gas was the same. Some textbooks called it ideal gas some textbooks particularly in physical chemistry used to call it a perfect gas. So in physical chemistry you have a perfect solution and the perfect crystal so maybe they like the word perfect. Later on I found that some textbook define an ideal gas the way we do and then what we call or what I have been calling ideal gas with constant specific heats they tend to define as a perfect gas. So there is no global definition I get a feeling ideal gas is a more common nomenclature and if you want to use perfect gas to mean something else or the same thing say so and use it that is it. Unfortunately the scientific community has not standardized nomenclatures and symbols except a few things like pressure, velocity, internal energy, entropy and enthalpy. Even availability, exergy these are not standardized over to you 1118 Sri Jayachama Rajendra College Mysore when you say open system and control volume are same can we consider control volume area to be a closed system. If so how both open system and control volume are similar see open system and control volume are synonyms they can be applied to any system through which a material can flow in or flow out particularly a fluid but it could be any other material if during a process some mass flows in or mass flows out or both we call it either a control volume or an open system. The traditional method was control mass and control volume the modern method is closed system and open system I think that should explain it by the way I have been frantically been informed that t is ready and we have to break.


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