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One experimental method of measuring an insulating material’s thermal
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An Introduction to Thermal Physics
- A box with a total surface area of 1.20 m and a wall thickness of 4.00 cm is made of an insulating material. A 10.0-W electric heater inside the box maintains the inside temperature at 15.0 °C above the outside temperature. Find the thermal conductivity k (in W/m. OC) of the insulating material. O 22.2 x 102 O1.11 x 10-2 O 2.22 x 10-2 O 4.44 x 10-2 O 11.2 x 10-2arrow_forwardA closed box is filled with dry ice at a temperature of -86.0 °C, while the outside temperature is 21.0 °C. The box is cubical, measuring 0.394 m on a side, and the thickness of the walls is 4.49 × 102 m. In one day, 3.76 × 106 J of heat is conducted through the six walls. Find the thermal conductivity of the material from which the box is made. Number Unitsarrow_forwardSamples A and B are at different initial temperatures when they are placed in a thermally insulated container and allowed to come to thermal equilibrium. Figure (a) gives their temperatures T versus time t. Sample A has a mass of 4.96 kg; sample B has a mass of 1.35 kg. Figure (b) is a general plot for the material of sample B. It shows the temperature change AT that the material undergoes when energy is transferred to it as heat Q. The change AT is plotted versus the energy Q per unit mass of the material, and the scale of the vertical axis is set by AT, = 4.80 °C. What is the specific heat of sample A? 100 AT, 60 20 10 20 8. 16 t (min) Q/m (kJ/kg) (a) (b)arrow_forward
- What is the rate of heat transfer in J/s through the body's skin and the fat layer just beneath its surface? Treat the skin and fat as a single layer that is 1.20 cm thick. Assume the temperature of the inner surface of the layer corresponds to internal body temperature, or 36.7 °C, and the temperature of the outer surface of the layer corresponds to skin temperature, or 34.0 °C. Take the total surface area of the layer to be 1.50 m² and use a value of 0.413 W/(m-C°) for the average thermal conductivity of the layer. Number Unitsarrow_forwardMonochromatic light (λ = 500 nm) is incident on a soap bubble (n = 1.40). What is the wavelength of the light (in nm) in the bubble film? Select one: O a. 255 O b. 700 O c. 357 O d. 422 O e. 500arrow_forwardSamples A and B are at different initial temperatures when they are placed in a thermally insulated container and allowed to come to thermal equilibrium. Figure (a) gives their temperatures T versus time t. Sample A has a mass of 5.37 kg; sample B has a mass of 1.64 kg. Figure (b) is a general plot for the material of sample B. It shows the temperature change AT that the material undergoes when energy is transferred to it as heat Q. The change AT is plotted versus the energy Q per unit mass of the material, and the scale of the vertical axis is set by AT, = 4.10 °C. What is the specific heat of sample A? 100 AT A 60 20 10 20 8. 16 t (min) Q/m (kJ/kg) (a) (b) Number i Units T (°C) AT (C°)arrow_forward
- Samples A and B are at different initial temperatures when they are placed in a thermally insulated container and allowed to come to thermal equilibrium. Figure (a) gives their temperatures T versus time t. Sample A has a mass of 4.79 kg; sample B has a mass of 1.50 kg. Figure (b) is a general plot for the material of sample B. It shows the temperature change AT that the material undergoes when energy is transferred to it as heat Q. The change AT is plotted versus the energy Q per unit mass of the material, and the scale of the vertical axis is set by AT, = 4.50 °C. What is the specific heat of sample A? Number i T (°C) 100 60 20 0 A Units 10 t (min) (a) 20 AT (Cº) AT, 0 8 Q/m (kJ/kg) (b) 16arrow_forwardA closed box is filled with dry ice at a temperature of -83.9 °C, while the outside temperature is 26.9 °C. The box is cubical, measuring 0.350 m on a side, and the thickness of the walls is 3.80 x 10-2 m. In one day, 3.35 x 106 J of heat is conducted through the six walls. Find the thermal conductivity of the material from which the box is made. Number 30251.3 Unitsarrow_forwardA copper bar is welded end to end to a bar of an unknown metal. The two bars have the same lengths and cross-sectional areas. The free end of the copper bar is maintained at a temperature TH that can be varied. The free end of the unknown metal is kept at 0.0∘C. To measure the thermal conductivity of the unknown metal, you measure the temperature T at the junction between the two bars for several values of TH. You plot your data as T versus TH both in kelvins, and find that your data are well fit by a straight line that has slope 0.460. What do your measurements give for the value of the thermal conductivity of the unknown metal? Use kCu = 385 W/(m⋅K) .arrow_forward
- A box with a total surface area of 1.20 m2 and a wall thickness of 4.00 cm is made of an insulting material. A 10.0 -W electric heater inside the box maintains the inside temperature at 15.0 °C above the outside temperature. Find the thermal conductivity k of the insulating material.arrow_forwardGeologists measure conductive heat flow out of the earth by drilling holes (a few hundred meters deep) and measuring the temperature as a function of depth. Suppose that in a certain location the temperature increases by 20°C per kilometer of depth and the thermal conductivity of the rock is 2.5 W/m·K. What is the rate of heat conduction per square meter in this location? Assuming that this value is typical of other locations over all of earth's surface, at approximately what rate is the earth losing heat via conduction? (The radius of the earth is 6400 km.)arrow_forwardThe thermal conductivities of human tissues vary greatly. Fat and skin have conductivities of about 0.20 W/m · K and 0.020 W/m · K respectively, while other tissues inside the body have conductivities of about 0.50 W/m · K. Assume that between the core region of the body and the skin surface lies a skin layer of 1.0 mm, fat layer of 0.50 cm, and 3.2 cm of other tissues. (a) Find the R-factor for each of these layers, and the equivalent R-factor for all layers taken together, retaining two digits. Rskin m2 · K/W Rfat m2 · K/W Rtissue m2 · K/W R m2 · K/W (b) Find the rate of energy loss when the core temperature is 37°C and the exterior temperature is 0°C. Assume that both a protective layer of clothing and an insulating layer of unmoving air are absent, and a body area of 2.0 m2. Warrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage Learning