A hollow cylinder has length L, inner radius a, and outer radius b, and the temperatures at the inner and outer surfaces are T2 and T1. (The cylinder could represent an insulated hot-water pipe.) The thermal conductivity of the material of which the cylinder is made is k. Derive an equation for (a) the total heat current through the walls of the cylinder; (b) the temperature variation inside the cylinder walls. (c) Show that the equation for the total heat current reduces to Eq. (17.21) for linear heat flow when the cylinder wall is very thin. (d) A steam pipe with a radius of 2.00 cm, carrying steam at 140C, is surrounded by a cylindrical jacket with inner and outer radii 2.00 cm and 4.00 cm and made of a type of cork with thermal conductivity 4.00 * 10-2 W>m # K. This in turn is surrounded by a cylindrical jacket made of a brand of Styrofoam with thermal conductivity 2.70 * 10-2 W>m # K and having inner and outer radii 4.00 cm and 6.00 cm (Fig. P17.115). The outer surface of the Styrofoam has a temperature of 15C. What is the temperature at a radius of 4.00 cm, where the two insulating layers meet? (e) What is the total rate of transfer of heat out of a 2.00-m length of pipe?

SI Leader is Andrew Bastien Email: abastian@uab.edu Syllabus is on Canvas Electricity, Magnetism and Optics overview (so we know why we’re learning this stuff) Check WebAssign for all homework assignments Keep in contact with any questions on homework, concepts, anything that you don’t understand. Student emails are something Dr. Rast likes laurenr@uab.edu Office Hours WF 1:30-2:30 or by appointment SI is highly recommended (don’t forsake it just so you can get a few more hours sleep this time) Class and recitation is NOT happening on MLK Day Monday, January 16, 2017 Lowest Recitation score is dropped No lab the first week of school Email Dr. Devore with lab questions; he runs all things involved with physics lab If you have an excused absence for class or recitation, email Dr. Rast with documentation Get the textbook this time Recitation really improves your overall course score Two in class tests each worth 15% Final exam grade replaces lowest exam grade WebAssign is 20% Class Key is uab 0085 5361 Final Exam is cumulative A is 88% and above Exam scores are scaled so the class average is 68-72 She never scales down You’re learning the foundations of physics reasoning Show your work on your tests (including on multiple choice problems) We will begin using iClicker in class Wednesday, January 18 Pretty much every modern technology depends on electricity, magnetism, and optics The mathematics and concepts of this stuff is more abstract However, it takes time to build up your intuition for it You should study for this as much as you studied