3. Metals have ............ thermal conductivity value compared to polymers. a. Low b. Very low c. High d. Medium 4. Determine the length of a copper wire that has a cross - sectional area as 8.1 mm2. The resistance and the electrical resistivity of the copper wire are 14 and 1.79 x 10-6 m. The length of a copper wire (in meters)

3. Metals have ............ thermal conductivity value compared to polymers. a. Low b. Very low c. High d. Medium 4. Determine the length of a copper wire that has a cross - sectional area as 8.1 mm2. The resistance and the electrical resistivity of the copper wire are 14 and 1.79 x 10-6 m. The length of a copper wire (in meters)

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.73P: Estimate the R-values for a 5-cm-thick fiberglass board and a 2.5-cm-thick polyurethane foam layer....

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Which of the following statements are true? Select one or more: a. Dislocations and defects make thermal transfer easy due to plastic deformation b. Starting at room temperature, the heat conductivity of ceramics goes generally up with increasing temperature c. Starting at room temperature, the heat conductivity of ceramics goes generally down with increasing temperature d. Dislocations and defects make thermal transfer difficult due to phonon scattering e. Heat transfer in solids occurs mainly by waves of atoms vibrating f. Heat transfer in solids occurs mainly by phonons
Question 5.1: A thermopile is constructed with chromel-alumel materials. Five junctions are maintained at 400-C and five junctions are maintained at 100°C. The output of the thermopile is connected to a potentiometer. Answer the following questions: a) Draw the equivalent circuit and indicate all the given information. b) What is the voltage induced by the potentiometer? Given: Table 8.30 Temperature. °C -150 -100 <-50 <<-25 0 25 50 75 100 150 200 300 400 500 600 800 1000 1200 1500 1750 Thermal emf in absolute millivolts for commonly used thermocouple combinations, according to ITS(90) (Reference junction of 0 C)¹ Copper vs. Constantan (7) -4.648 -3.379 -1.819 -0.940 0 0.992 2.036 3.132 4.279 6.704 9.288 14.862 20.872 Chromel vs. Constantan (E) -7.279 -5.237 -2,787 -1.432 0 1.495 3.048 4.657 6.319 9.789 13.421 21.036 28.946 37.005 45.093 61,017 76.373 Iron vs. Constantan ( -6.500 -4.633 -2.431 -1.239 ( 1.277 2.585 3.918 5.269 8.010 10.779 16.327 21.848 27.393 33.102 45.494 57.953…
b) A 1.25 m long cable has a diameter 3.50 mm with a Young's Modulus, E, of 9.75 x 10⁹ N/m². When the wire is placed under tension, it experiences a stress of 202.52 x 106 N/m², the length of the cable extends by 36.35 mm. Calculate the force that the cable experiences under tension and the strain energy density (U/V) due to deformation. Give your answers in newtons (N) to 2 decimal places for the force; and in joules per cubic metre (J/m³) for the strain energy density to 2 decimal places. Assume the cable is solid and the material is homogeneous. c) Figure Q1c shows a bracket on rollers that allow the bracket to move along a beam in the horizontal direction. A force F₁ of 2625 N acts at point A where the angle between F, and the x-axis is 100. If force F₂ acts at an angle a = 400 between F2 and the y-axis: (i) Determine the magnitude of F2 necessary to maintain bracket on horizontal equilibrium. (ii) Determine the vertical force at A acting along the y-axis. Give your answers to the…
6. State three reasons why the thermal conductivity value (for a particular material) is important in engineering?
In mechanical resistance
Using the data in Table 18.1, (a) calculate the resistance of an aluminum wire with 5 mm diameter and 5 m length. (b) What is the current flow if the potential drop across the ends of the wire is 0.04 V? Table 18.1 Room-Temperature Electrical Conductivities for Nine Common Metals and Alloys Electrical Conductivity [(N-m)-'] Metal 6.8 × 107 6.0 × 107 4.3 × 107 3.8 × 107 1.6 × 107 1.0 × 107 0.94 × 107 0.6 × 107 0.2 × 107 Silver Copper Gold Aluminum Brass (70Cu–30ZN) Iron Platinum Plain carbon steel Stainless steel
Requirements: 1. Fill the tables. 2. Calculate the thermal conductivity and the thermal resistance. Comment on results. 3. Plot the measured values for temperature difference over the electrical power. please don't reject the question. Thank you
Two wires of equal lengths, one Aluminum, and the other steel, were stretched the same amount under an applied load P. The modulus of elasticity for Aluminum and steel are 80 GPa, 200 GPa respectively, what is the diameter ratio of the Aluminum wire with respect to steel? Aluminum alloy wire Steel wire 'P P Select one: a. 2.50 b. 1.63 O c. 0.40 O d. 1.58 O e. 0.63 O f. None
M4.25 (Sl units) What is the resistance R of a length of copper wire whose length 10 m and whose diameter 0.30 mm? Use Table 4.3 of the book for reference. Round to the nearest thousandth of an ohm ()
1. A room has a pine ceiling (k = 0.12 WI(m-Cº) ] that measures 3.0 m x 4.0 m 2.0 cm. On a cold day, the temperature inside the room is 20°C, and the temperature in the attic above is 8°C. If 6.0 cm of glass wool insulation ( k = 0.042 WI(m.Cº) ] were put in above the ceiling, how much energy would be saved in one hour? 2. 2.0-kg block moving with an initial speed of 5 m/s slides on a rough table and is stopped by the force of friction. Assuming that the table and air remain at 24°C, calculate the entropy change of the universe.
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Can you please tell me which ones are true and which ones are false ? a- Amorphous and semi-crystalline polymers both become brittle at lower temperatures b- Localized heating at high frequencies results in polymer softening causing polymer fatigue c- The elastic modulus of semi-crystalline polymers rises as chain entanglement decreases d-Polymers are similar to metals in that they can also exhibit both ductile and brittle fracture e- Phonons scatter from dislocations in metals, reducing heat transfer efficiency f- The maximum phonon energy is limited by the interatomic lattice spacing g- Phonons arise from excitation of electrons to higher energy levels in an atom h- Increased temperature in many ceramics up to around 1000 °C leads to a decrease in thermal conductivity