Tuesday, March 17, 2020

Table of Electrical Resistivity and Conductivity

Table of Electrical Resistivity and Conductivity This table presents the  electrical resistivity and electrical conductivity of several materials.   Electrical resistivity, represented by the Greek letter Ï  (rho), is a measure of how strongly a material opposes the flow of electric current. The lower the resistivity, the more readily the material permits the flow of electric charge. Electrical conductivity is the reciprocal quantity of resistivity. Conductivity is a measure of how well a material conducts an electric current. Electric conductivity may be represented by the Greek letter ÏÆ' (sigma), ÃŽ º (kappa), or ÃŽ ³ (gamma). Table of Resistivity and Conductivity at 20 °C Material Ï  (ÃŽ ©m) at 20  °CResistivity ÏÆ' (S/m) at 20  °CConductivity Silver 1.59Ãâ€"10−8 6.30Ãâ€"107 Copper 1.68Ãâ€"10−8 5.96Ãâ€"107 Annealed copper 1.72Ãâ€"10−8 5.80Ãâ€"107 Gold 2.44Ãâ€"10−8 4.10Ãâ€"107 Aluminum 2.82Ãâ€"10−8 3.5Ãâ€"107 Calcium 3.36Ãâ€"10−8 2.98Ãâ€"107 Tungsten 5.60Ãâ€"10−8 1.79Ãâ€"107 Zinc 5.90Ãâ€"10−8 1.69Ãâ€"107 Nickel 6.99Ãâ€"10−8 1.43Ãâ€"107 Lithium 9.28Ãâ€"10−8 1.08Ãâ€"107 Iron 1.0Ãâ€"10−7 1.00Ãâ€"107 Platinum 1.06Ãâ€"10−7 9.43Ãâ€"106 Tin 1.09Ãâ€"10−7 9.17Ãâ€"106 Carbon steel (1010) 1.43Ãâ€"10−7 Lead 2.2Ãâ€"10−7 4.55Ãâ€"106 Titanium 4.20Ãâ€"10−7 2.38Ãâ€"106 Grain oriented electrical steel 4.60Ãâ€"10−7 2.17Ãâ€"106 Manganin 4.82Ãâ€"10−7 2.07Ãâ€"106 Constantan 4.9Ãâ€"10−7 2.04Ãâ€"106 Stainless steel 6.9Ãâ€"10−7 1.45Ãâ€"106 Mercury 9.8Ãâ€"10−7 1.02Ãâ€"106 Nichrome 1.10Ãâ€"10−6 9.09Ãâ€"105 GaAs 5Ãâ€"10−7 to 10Ãâ€"10−3 5Ãâ€"10−8 to 103 Carbon (amorphous) 5Ãâ€"10−4 to 8Ãâ€"10−4 1.25 to 2Ãâ€"103 Carbon (graphite) 2.5Ãâ€"10−6 to 5.0Ãâ€"10−6 //basal plane3.0Ãâ€"10−3 ⊠¥basal plane 2 to 3Ãâ€"105 //basal plane3.3Ãâ€"102 ⊠¥basal plane Carbon (diamond) 1Ãâ€"1012 ~10−13 Germanium 4.6Ãâ€"10−1 2.17 Sea water 2Ãâ€"10−1 4.8 Drinking water 2Ãâ€"101 to 2Ãâ€"103 5Ãâ€"10−4 to 5Ãâ€"10−2 Silicon 6.40Ãâ€"102 1.56Ãâ€"10−3 Wood (damp) 1Ãâ€"103 to 4 10−4 to 10-3 Deionized water 1.8Ãâ€"105 5.5Ãâ€"10−6 Glass 10Ãâ€"1010 to 10Ãâ€"1014 10−11 to 10−15 Hard rubber 1Ãâ€"1013 10−14 Wood (oven dry) 1Ãâ€"1014 to 16 10−16 to 10-14 Sulfur 1Ãâ€"1015 10−16 Air 1.3Ãâ€"1016 to 3.3Ãâ€"1016 3Ãâ€"10−15 to 8Ãâ€"10−15 Paraffin wax 1Ãâ€"1017 10−18 Fused quartz 7.5Ãâ€"1017 1.3Ãâ€"10−18 PET 10Ãâ€"1020 10−21 Teflon 10Ãâ€"1022 to 10Ãâ€"1024 10−25 to 10−23 Factors That Affect Electrical Conductivity There are three main factors that affect the conductivity or resistivity of a material: Cross-Sectional Area: If the cross-section of a material is large, it can allow more current to pass through it. Similarly, a thin cross-section restricts current flow.Length of the Conductor: A short conductor allows current to flow at a higher rate than a long conductor. Its a bit like trying to move a lot of people through a hallway.Temperature: Increasing temperature makes particles vibrate or move more. Increasing this movement (increasing temperature) decreases conductivity because the molecules are more likely to get in the way of current flow. At extremely low temperatures, some materials are superconductors. Resources and Further Reading MatWeb Material Property Data.Ugur, Umran. Resistivity of steel. Elert, Glenn (ed), The Physics Factbook, 2006.Ohring, Milton. Engineering Materials Science. New York: Academic Press, 1995.  Pawar, S. D., P. Murugavel, and D. M. Lal. Effect of Relative Humidity and Sea Level Pressure on Electrical Conductivity of Air over Indian Ocean. Journal of Geophysical Research: Atmospheres 114.D2 (2009).

Sunday, March 1, 2020

Uranium in a Nutshell

Uranium in a Nutshell Uranium is an extremely heavy metal, but instead of sinking into the Earths core it is concentrated on the surface. Uranium is found almost exclusively in the Earths continental crust, because its atoms dont fit in the crystal structure of the minerals of the mantle. Geochemists consider uranium one of the incompatible elements, more specifically a member of the large-ion lithophile element or LILE group. Its average abundance, over the whole continental crust, is a bit less than 3 parts per million. Uranium never occurs as bare metal; rather, it most often occurs in oxides as the minerals uraninite (UO2) or pitchblende (partially oxidized uraninite, conventionally given as U3O8). In solution, uranium travels in molecular complexes with carbonate, sulfate and chloride as long as the chemical conditions are oxidizing. But under reducing conditions, uranium drops out of solution as oxide minerals. This behavior is the key to uranium prospecting. Uranium deposits mainly occur in two geologic settings, a relatively cool one in sedimentary rocks and a hot one in granites. Sedimentary Uranium Deposits Because uranium moves in solution under oxidizing conditions and drops out under reducing conditions, it tends to gather where oxygen is absent, such as in black shales and other rocks rich in organic material. If oxidizing fluids move in, they mobilize the uranium and concentrate it along the front of the moving fluid. The famous roll-front uranium deposits of the Colorado Plateau are of this type, dating from the last few hundred million years. The uranium concentrations are not very high, but they are easy to mine and process. The great uranium deposits of northern Saskatchewan, in Canada, are also of sedimentary origin but with a different scenario of much greater age. There an ancient continent was deeply eroded during the Early Proterozoic Era some 2 billion years ago, then was covered by deep layers of sedimentary rock. The unconformity between the eroded basement rocks and overlying sedimentary basin rocks is where chemical activity and fluid flows concentrated uranium into orebodies reaching 70 percent purity. The Geological Association of Canada has published a thorough exploration of these unconformity-associated uranium deposits with full details of this still-mysterious process. At roughly the same time in geologic history, a sedimentary uranium deposit in present-day Africa actually grew concentrated enough that it ignited a natural nuclear reactor, one of Earths neatest tricks. Granitic Uranium Deposits As large bodies of granite solidify, the trace amounts of uranium become concentrated in the last bits of fluid left. Especially at shallow levels, these may fracture and invade surrounding rocks with metal-bearing fluids, leaving veins of ore. More episodes of tectonic activity can concentrate these further, and the worlds largest uranium deposit is one of these, a hematite breccia complex at Olympic Dam in South Australia. Good specimens of uranium minerals are found in the final stage of granite solidification- the veins of large crystals and unusual minerals called pegmatites. There may be found cubic crystals of uraninite, black crusts of pitchblende and plates of uranium-phosphate minerals such as torbernite (Cu(UO2)(PO4)2Â ·8–12H2O). Silver, vanadium and arsenic minerals are also common where uranium is found. Pegmatite uranium is not worth mining today, because the ore deposits are small. But they are where the good mineral specimens are found. The radioactivity of uranium affects the minerals around it. If you are examining a pegmatite, these signs of uranium include blackened fluorite, blue celestite, smoky quartz, golden beryl and red-stained feldspars. Also, chalcedony that contains uranium is intensely fluorescent with a yellow-green color. Uranium in Commerce Uranium is prized for its enormous energy content, which can be harnessed to generate heat in nuclear reactors or unleashed in nuclear explosives. The Nuclear Nonproliferation Treaty and other international agreements govern traffic in uranium to ensure that it is used only for civilian purposes. World trade in uranium amounts to more than 60,000 metric tons, all of it accounted for under international protocols. The largest producers of uranium are Canada, Australia and Kazakhstan. The price of uranium has fluctuated with the fortunes of the nuclear power industry and the military needs of various countries. After the collapse of the Soviet Union, large stores of enriched uranium have been diluted and sold as nuclear fuel under the Highly Enriched Uranium Purchase Agreement, which kept prices low through the 1990s. As of about 2005, however, prices have been climbing and prospectors are out in the field again for the first time in a generation. And with renewed attention on nuclear power as a zero-carbon energy source in the context of global warming, it is time to become familiar again with uranium.

Friday, February 14, 2020

Teaching Literary Strategies in Children's Books Essay

Teaching Literary Strategies in Children's Books - Essay Example Nodelman and Mavis also state that there are many strategies that can be used in order to help children become aware of good literature. According to these authors, the children are helped even more if they also enjoy literature; if they do, they are able to teach their students better. 1.1 What to Teach Nodelman and Reimer suggest that teachers must teach their students the techniques that people who read literature on a regular basis use (34). This basically means that children must learn how to interact with literature by making good choices of what to read and by being motivated to read, because what they read is interesting. As an example, in this author’s opinion, one of the reasons the Harry Potter books became so popular was because children of all ages (including adults) could read and enjoy the books. Readers were motivated to read each book as it came out because J.K. Rowling left something for readers to wonder about at the end of each book. The books are fun, inte resting, and they make the reader want to go to the land of Hogwarts. For some children and adults, Harry Potter may have created an interest in other book series like the Hobbit or Narnia books because they were also interesting and able to take the reader into these far away lands. The research done by Nodelman and Reimer provide several ideas for teaching literary strategies that they learned from observing children and teachers in Britain. Some of these were: Children need to have a variety of literature to read in their homes and parents need to love and read literature also to set the example. Children need to be able to read a variety of literature from comic books to nonfiction and fiction. Teachers should allow students to choose from a variety of literature in their classrooms and children should have a say in the books they want to discuss in class. Parents can encourage their children by becoming familiar with the books their children are reading and talking to them abou t the books. These are a few of the many tips that are available to help teach a love of literature to children. The rest of this research paper will discuss a variety of strategies that have been used to teach this topic. 2 Teacher Strategies for Teaching Literature Helping children learn is a major reason to promote the teaching of literature. The reason literature is important is because it can be used to teach across the curriculum. This discussion begins with Gail Goss, a teacher who combines children’s literature and her students’ interests to help them learn easier. Goss suggests an interdisciplinary approach because it: 1. Increases the student’s curiosity in a subject and makes them want to read. 2. By using several content areas, students make a connection between any of their subjects. 3. This allows the teacher to provide â€Å"real world† activities like â€Å"researching, collecting and synthesizing data †¦ narrative reports, and it he lps to connect students with real world situations† (Goss 4). Goss uses the theme of cats to work with her students and uses a variety of literature about cats. As an example, she uses the books Puss ad Boots and Cats of Myth to teach grammar. Children

Saturday, February 1, 2020

Florida v. Jardines, 11-564 from the Supreme Court in March 2013 Research Paper

Florida v. Jardines, 11-564 from the Supreme Court in March 2013 - Research Paper Example nt amount of marijuana and evidence that he was a drug trafficker too, Jardines contested the warrant saying that it is was breach of the fourth amendment. Hence, rendering the raid, and the consequence (charges for possessing marijuana), null and void. The Supreme Court of Florida approved the decision of the trial court, holding that the evidence be suppressed as the officers had committed Fourth Amendment breach. They did not have a probable cause to search Jardines’ property (Florida v. Jardines, 2013). 5. Rationale: why did the court decide the case this way? Was there a decent? A concurring opinion? How many Justices voted with the majority? What were the reasons that different judges felt differently about parts of the case? The court is not a law machine set out to operate under given set of command. The law and courts operate to contribute towards a better society. The law is made to protect the citizen and not to harass them. The notion that no one should be held above the law needs to be practiced in such a way as decided the Supreme Court of Florida. The Fourth amendment upholds that the people have a right to be secure in their homes (Jardines v. State, 2011). The Fourth Amendment does not allow police or anyone to search someone’s property without probable cause. The term ‘search’ has been highlighted in the Fourth Amendment as when governments physically intrudes someone’s property (person, papers, houses or effects) it is a ‘search’ (Florida v. Jardines, 2013).. The citizens should consider home as safe from unreasonable investigations. If this sense of security is not provided to the citizens then the society will always feel vulnerable and under pressure of the government. The officers that searched Jardines’ house did not ‘see’ anything with their own eyes before entering his premises. There was apparently no suspicious activity around or in his house. Had the officers seen something then it would have been a reasonable

Friday, January 24, 2020

The Effect of Catalyst an the Rate Of Reaction Essay -- GCSE Chemistry

The Effect of Catalyst an the Rate Of Reaction Chemistry Coursework Does The Number of Drops of Catalyst Effect The Rate Of Reaction Candidate Name: Ben Dodds Candidate Number: 7158 School: Oundle School Completion Date: Introduction We are studying the reaction between zinc and sulphuric acid, the reaction is catalysed by copper sulphate and this experiment is to test whether the amount of drops effect the rate of reaction. Word Equation Zinc(s) + Sulphuric acid(aq) Ã   Hydrogen(g) + Zinc Sulphate(aq) Symbol Equation Zn + H2SO4 Ã   H + ZnSO4 This reaction is catalysed by Copper sulphate (CuSO4) Ionic Equation - Cancel Spectator ion (SO42-) Zn + 2H+ Ã   Zn2+ + H2 For this reaction to work there must be hard collisions between the zinc and the hydrogen ions (acidity ion) from the acid, The faster the harder and the more often the collisions happen so I predict the more catalyst the faster the reaction. Planning Safety * Sulphuric acid at 2M is a corrosive substance but diluted to 1M it is an Irritant, so wear a Lab coat to protect your cloths and wear safety specs to protect your eyes. * Zinc is very flammable so do not put a Bunsen burner near it. * Copper sulphate is very nasty and corrosive when it gets in your eyes so wear safety specs. * Hydrogen is explosive when mixed with oxygen and burnt; so don't use a Bunsen burner near the experiment. Method ====== First a clamp stand was taken and a gas cyringe was fitted so that when it is connected to a conicle flask the conicle flask will touch the bench. 1 gram of zinc was taken along with 2M sulphuric acid and distilled sollutions. The solutions were mixed to form 1 M acid and a certain number of dfrops of catalyst wes added in the conicle flask and the... ...zincand the amount of copper sulphate were not kept constant. Did I do enough readings I think I have done enough readings as the trend of my predictions were there but I could have done a greater range. The only problem with that is I would have to dilute the acid again as the times were very quick for 15 seconds so it would be to awkward to collect if I did 30 drops of copper suphate it would have been to quick to record. Could your results lead to any findings outside the range of results covered? Yes I could as my graph is a straight line graph so I could extend it and look at maybe 40 or 50 drops and look at what the rate is for them What additional relevant work could you do to extend your theory? We chose to vary the amount of drops of catalyst but what you could vary is maybe whether the temperature, pressure, concentration of the acid or amount of zinc.

Thursday, January 16, 2020

Centralized Organizational Structure Essay

ABC Homecare is a growing company consisting of four different departments. Each department has a director who makes all of the daily decisions from patient enrollment to employee breaks. This type of structure worked well when the company was established in 1989 since it only consisted of 30 employees total. ABC Homecare has grown to over 150 employees and needs change. The centralized structure has been successful for the Directors of the company, however, often leaves employees and managers unhappy. This structure is popular for producing â€Å"sluggish† business operations since ultimately only one person is making the final decision (Vitez, 2013). Currently we have 7 employee complaints on file for issues regarding our structure. Formal versus Informal Organization Reports have indicated that attendance in our formal organization groups have decline drastically over the past six months. Many employees have joined the smaller, informal groups to voice concerns and suggestions. Although we are happy that employee voices are still exercised, they are not getting the level of satisfaction needed according to the employee and this is for a number of reasons. Employees are using their voices in informal settings that do not have all of the features of actual formal organizations. In a formal group several features are characterized: a common goal; an accepted pattern of purpose †¢ a set of shared values or common beliefs that give individuals a sense of identification and belonging †¢ continuity of goal-oriented interaction †¢ a division of labor deliberately planned to achieve the goal †¢ a system of authority or a chain of command to achieve conscious integration of the group and conscious coordination of efforts to reach the goal (Liebler & McConnell, 2013 p. 67). Without these features, informal groups only serve to clarify any misunderstanding from a formal organization or allow for socialization informally. Although ABC Homecare has been voted one of the best homecare agencies in our area, there is room for improvement. Patient satisfaction is greatly affected by employee satisfaction so a plan must be implemented soon to ensure that our employees are happy to work for our company and remain as such.

Wednesday, January 8, 2020

Delphi problem TForm.Create() -- Nil, Self or Application

When you create  Delphi objects dynamically  that inherit from TControl, such as a TForm (representing a form/window in Delphi applications), the constructor Create expects an Owner parameter: constructor Create(AOwner: TComponent) ; The AOwner parameter is the owner of the TForm object. The owner of the form is responsible for freeing the form -- i.e., memory allocated by the form -- when needed. The form appears in the Components array of its owner and it is destroyed automatically when its owner is destroyed.   You have three choices for the AOwner parameter: Nil, self, and application. To understand the answer, you first need to know the meaning of nil, self and Application. Nil  specifies that no object owns the form and therefore the developer is responsible for freeing the created form (by calling myForm.Free when you no longer need the form)Self  specifies the object in which the method is called. If, for example, you are creating a new instance of a TMyForm form from inside a buttons OnClick handler (where this button is placed on a MainForm), self refers to MainForm. Thus, when the MainForm is freed, it will also free MyForm.Application specifies a global TApplication type variable created when you run your application. Application encapsulates your application as well as providing many functions that occur in the background of the program. Examples: Modal forms. When you create a form to be displayed modally and freed when the user closes the form, use nil as the owner: var myForm : TMyForm; begin  Ã‚  myForm : TMyForm.Create(nil) ;  Ã‚  try  Ã‚  Ã‚  Ã‚  myForm.ShowModal;  Ã‚  finally  Ã‚  Ã‚  Ã‚  myForm.Free;  end; end;Modeless forms. Use Application as the owner:varmyForm : TMyForm;...myForm : TMyForm.Create(Application) ; Now, when you terminate (exit) the application, the Application object will free the myForm instance. Why and when is TMyForm.Create(Application) NOT recommended? If the form is a modal form and will be destroyed, you should pass nil for the owner. You could pass application, but the time delay caused by the notification method being sent to every component and form owned or indirectly owned by the Application could prove disruptive. If your application consists of many forms with many components (in the thousands), and the form youre creating has many controls (in the hundreds), the notification delay can be significant. Passing nil as the owner instead of application will cause the form to appear sooner, and will not otherwise affect the code. However, if the form you need to create is not modal and is not created from the applications main form, then when you specify self as the owner, closing the owner will free the created form. Use self when you dont want the form to outlive its creator. Warning: To dynamically instantiate a Delphi component and explicitly free it sometime later, always pass nil as the owner. Failure to do so can introduce unnecessary risk, as well as performance and code maintenance problems. In SDI applications, when a user closes the form (by clicking on the [x] button) the form still exists in the memory -- it only gets hidden. In MDI applications, closing an MDI child form only minimizes it.The OnClose event provides an Action parameter (of the TCloseAction type) you can use to specify what happens when a user attempts to close the form. Setting this parameter to caFree will free the form. Delphi tips navigator: » Get the full HTML from the TWebBrowser component « How to Convert Pixels to Millimeters