(1) Suppose a person is covered head to foot by wool clothing with average thickness of 2 cm and is transferring energy of 6000 joules by conduction through the clothing for 2 minutes. What is the temperature difference across the clothing, given the surface area is 1.4m2? (Given: Thermal conductivity of wool is 0.04 W/mK) The difference in temperature =

(1) Suppose a person is covered head to foot by wool clothing with average thickness of 2 cm and is transferring energy of 6000 joules by conduction through the clothing for 2 minutes. What is the temperature difference across the clothing, given the surface area is 1.4m2? (Given: Thermal conductivity of wool is 0.04 W/mK) The difference in temperature =

College Physics

11th Edition

ISBN:9781305952300

Author:Raymond A. Serway, Chris Vuille

Publisher:Raymond A. Serway, Chris Vuille

Chapter1: Units, Trigonometry. And Vectors

Section: Chapter Questions

Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...

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Estimate the number of panels in an array required to supply hot water to a summer home if 100 gal of tap water per day are to be heated from 10 to 50°C. Assume that the average efficiency of the array is 60 percent and that the average daily insolation intercepted by the array is 5 kw-hr/m²-day. Each panel has an area of 1.5 m². Consider an array of nine panels arranged in three parallel strings. Each string has three panels in series. Water flows into the array at 0.03 kg/sec and divides equally into each string. The water enters the array at 10°C and leaves at 50°C. The first panel of each string raises the temperature by 20°C; the second, by 15°C; and the third, by 5°C. The area of each panel is 1.5 m² and the intercepted insolation is 800 W/m². (a) Find the efficiency of each panel of the array. (b) Find the rate at which heat is collected by the array. (c) Determine the overall efficiency of the array.
The next four questions use this description. Our Sun has a peak emission wavelength of about 500 nm and a radius of about 700,000 km. Your dark-adapted eye has a pupil diameter of about 7 mm and can detect light intensity down to about 1.5 x 10-11 W/m2. Assume the emissivity of the Sun is equal to 1. First, given these numbers, what is the surface temperature of the Sun in Kelvin to 3 significant digits? What is the power output of the Sun in moles of watts? (in other words, take the number of watts and divide it by Avogadro's number) Assuming that all of the Sun's power is given off as 500 nm photons*, how many photons are given off by the Sun every second? Report your answer to the nearest power of 10 (e.g. if you got 7 x 1024, give your answer as 25).
Compute the energy consumption in units of joules per year, gigawatts (GW), and watts per person as (a) fuel, (b) food, and (c) solar radiation for a country of population density 20 person/km2, an area of 1 million km2, and a fuel energy consumption rate of 250 GJ per person per year. Solar radiation reaching the ground is approximately 150 W/m2. The average person consumes food containing 2000 “calories” per day (1 calorie = 4182 J).
1) The walls of a house are 11 cm thick and have an average thermal conductivity two times that of cork. The walls' surface area is 850000 cm2 and their inside surface is at 18°C, while their outside surface is at 4°C. (Thermal conductivity of cork is 0.036 W/m°C). Calculate, (i) The rate of heat conduction through house walls in Watts: (1) Amount of heat conducted in Joules, in 5 min: 2) A spherical infrared heater of radius 6.5 cm and an emissivity of 0.82 radiates 0.48 kW of power. Given, Stefan's constant = 5.67x10 Wm K Calculate, Temperature of the heater in Celsius: 1) A 275-turns square loop of 34 cm on a side, carrying a current of 22 A creates a torque of 385 N m when the plane of the coil makes an angle 38° with the magnetic field.
Assume that the total surface area of a person's body is 1.4 m2 and his skin temprature is 10.6 °C (Assume his body acts as black body) If the temprature of surrounding is 35.2 °C, what is his net rate of heat loss by radiation? (Answer in one decimal places)
Suppose a walrus transfers energy by conduction through its blubber at the rate of 165 W when immersed in -0.95°C water. The walrus’s internal core temperature is 37.0°C, and it has a surface area of 2.1 m2 What is the average thicness of its blubber, in centimeters, which has the conductivity of fatty tissue?
On a day where the air temperature is 5.2 °C, the wind starts to blow, which increases the surface transfer co-efficient from 10 to 13.9 watts per metre-squared-Kelvin. For a human body with skin temperature 34°C and surface area 1.5 square metres, what is the wind-chill temperature? Answer: Check
Thermography is a technique for measuring radiant heat and detecting variations in surface temperatures that may be medically, environmentally, or militarily meaningful.(a) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 33.0C, such as on a person’s skin? (b) What is the percent increase in the rate of heat transfer by radiation from a given area at a temperature of 34.0C compared with that at 20.0C, such as for warm and cool automobile hoods?
A) Estimate the total solar heating absorbed by the Earth every second. Assume 36% of the incoming solar radiation is reflected by clouds and lost. You can assume that the Earth intercepts sunlight with an effective area of πr2 where r is Earth’s radius. B) Estimate the total heat lost by the Earth as infrared radiation every second. Assume Earth has an effective temperature of 252 K (-21 C).
What is the change in length of a 3.4-cm-long column of mercury if its temperature changes from 35 ºC to 35.3 ºC, assuming the mercury is unconstrained? The thermal coefficient of expansion of mercury is 6×10-5 /oC.
(a) Calculate the rate of heat conduction through house walls that are 13.0 cm thick and that have an average thermal conductivity twice that of glass wool. Assume there are no windows or doors. The surface area of the walls is 120m^2 and their inside surface is at 18.0ºC, while their outside surface is at 5.00ºC. (b) How many 1-kW room heaters would be needed to balance the heat transfer due to conduction?
The Sun radiates like a perfect black body with an emissivity of exactly 1. (a) Calculate the surface temperature of the Sun, given that it is a sphere with a 7.00×10^8-m radius that radiates 3.80×10^26 W into 3-K space. (b) How much power does the Sun radiate per square meter of its surface? (c) How much power in watts per square meter is that value at the distance of Earth, 1.50×10^11 m away? (This number is called the solar constant.)