Concept explainers
(a)
The power delivered by the power supply for each measurement in Table 28.4.
(a)
Answer to Problem 58PQ
The power delivered by the power supply for each measurement in Table 28.4 is shown in Table 1.
Explanation of Solution
Power delivered by the power supply is the same as the power radiated by the bulb. The expression for power is given by,
Here,
Conclusion:
The power delivered by the power supply for each measurement in Table 28.4 is shown in Table 1.
Table 1
Bulb A (carbon) | Bulb B (tungsten) | ||||
Therefore, the power delivered by the power supply for each measurement in Table 28.4 is shown in Table 1.
(b)
The temperature of each filament for each entry in the table Table 28.4.
(b)
Answer to Problem 58PQ
The temperature of each filament for each entry in the table Table 28.4 is shown in Table 2.
Explanation of Solution
Given that the emissivity of filaments is
Write the Stefan-Boltzmann equation for the power.
Here,
Write the expression for the surface area of the filament.
Here,
Use equation (III) in (II) and solve for
Conclusion:
Substitute
The power corresponding to each measurement is calculated in part (a), so that the above equation can be utilized to compute the temperatures corresponding to each entry. Ii is tabulated in Table 2.
Table 2
Bulb A (carbon) | Bulb B (tungsten) | ||||||
Therefore, the temperature of each filament for each entry in the table Table 28.4 is shown in Table 2.
(c)
The plot of
(c)
Answer to Problem 58PQ
The plot of
Explanation of Solution
The computed values of power
Conclusion:
Therefore, the plot of
Want to see more full solutions like this?
Chapter 28 Solutions
Physics for Scientists and Engineers: Foundations and Connections
- You extend an impromptu invitation to a friend for dinner. The only food you have is a couple of frozen steaks. You wish to defrost the steaks before grilling them. You defrost one by using your microwave oven, and you defrost the other by placing it in a bowl of very warm water. In each case, decide whether heat is transferred by conduction, convection, radiation, or some combination of these mechanisms. Explain your answers.arrow_forwardThe surface area of an unclothed person is 1.50 m2, and his skin temperature is 33.0C. The person is located in a dark room with a temperature of 20.0C, and the emissivity of the skin is e = 0.95. (a) At what rate is energy radiated by the body? (b) What is the significance of the sign of your answer?arrow_forwardConsider a 1000-W iron whose base plate is made of 0.5-cm-thick aluminum alloy 2024-T6 (r = 2770 kg/m3 and cp = 875 J/kg·°C). The base plate has a surface area of 0.03 m2. Initially, the iron is in thermal equilibrium with the ambient air at 22°C. Assuming 90 percent of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200°C.arrow_forward
- An electronic package with a surface area of 1 m2 placed in an orbiting space station is exposed to space. The electronics in this package dissipate all 1 kW of its power to the space through its exposed surface. The exposed surface has an emissivity of 1.0 and an absorptivity of 0.25. Determine the steady state exposed surface temperature of the electronic package (a) if the surface is exposed to a solar flux of 750 W/m2, and (b) if the surface is not exposed to the sun.arrow_forwardA 2.1-m-long, 0.2-cm-diameter electrical wire extends across a room that is maintained at 20°C. Heat is generated in the wire as a result of resistance heating, and the surface temperature of the wire is measured to be 180°C in steady operation. Also, the voltage drop and electric current through the wire are measured to be 110 V and 3 A, respectively. Disregarding any heat transfer by radiation, determine the convection heat transfer coefficient for heat transfer between the outer surface of the wire and the air in the room.arrow_forwardThe Sun has a diameter of approximately 1.4 x 109 m and a surface temperature of about 5650 C. Assuming that the Sun radiates as a blackbody with emissivity of unity, calculate the power radiated by the Sun into the solar system, which you can assume is at the temperature of the microwave background radiation.arrow_forward
- A plane brick wall (k = 0.7 W/m⋅K) is 10 cm thick. The thermal resistance of this wall per unit of wall area is a. 0.524 m2⋅K/W b. 0.250 m2⋅K/W c. 0.327 m2⋅K/W d. 0.143 m2⋅K/W e. 0.448 m2⋅K/Warrow_forwardThe heat flux in an aluminum pan containing boiling water is 5 × 10^5 W/m2. The temperature of the surface of the pan in contact with boiling water is 119 °C. a) Determine the temperature gradient in the pan on this surface. b) Determine an equation for calculating the temperature of the surface that is not in contact with water as a function of the thickness of the pan. c) What will be the temperature on the surface that is not in contact with water if the thickness of the pan is 1.2 mm? What if it's 4.0 mm? d) Evaluating the results obtained in questions "a", "b" and "c", how does the thickness of the pan influence the temperature gradient?arrow_forwardA spherical interplanetary probe, with a diameter of 2 m, is sent out into the solar system. The probe surface is made of material having an emissivity of 0.9 and an absorptivity of 0.1. Signals from the sensors monitoring the probe surface temperatures are indicating an average value of −40°C for a space temperature of 0 K. If the electronics inside the probe is generating heat at a rate of 100 W/m3, determine the incident radiation rate on the probe surface.arrow_forward
- A family comes home from a long vacation with laundry to do and showers to take. The water heater has been turned off during the vacation. If the heater has a capacity of 50.0 gallons and a 4800-W heating element, how much time is required to raise the temperature of the water from 20.0°C to 60.0°C? Assume the heater is well insulated and no water is withdrawn from the tank during that time.arrow_forwardA heating coil inside an electric kettle delivers 2.1kW of electric power to the water in the kettle. How long will it take to raise the temperature of 0.5kg of water from 20C to 100C?arrow_forwardTwo black parallel rectangles with dimensions 3 ft * 5 ft are spaced apart by a distance of 1 ft. The two parallel rectangles are experiencing radiation heat transfer as black surfaces, where the top rectangle receives a total of 180,000 Btu/h radiation heat transfer rate from the bottom rectangle. If the top rectangle has a uniform temperature of 60°F, determine the temperature of the bottom rectangle.arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningModern PhysicsPhysicsISBN:9781111794378Author:Raymond A. Serway, Clement J. Moses, Curt A. MoyerPublisher:Cengage Learning
- Physics for Scientists and EngineersPhysicsISBN:9781337553278Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPrinciples of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers with Modern ...PhysicsISBN:9781337553292Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning