Q5. The intensity of the solar radiations striking the PV panel of a solar powered car is found to be 900W/m2 and the dimensions of the PV panel fixed over the roof of a solar powered car is given below. Assuming efficiency of the PV panel to be 30% solar p.v 2.2 m (a) Find the area of PV panel fixed over the roof of the car? (b) Calculate the power of incident solar radiations? (e) Find the power out of the PV panel? 1.1m

Q5. The intensity of the solar radiations striking the PV panel of a solar powered car is found to be 900W/m2 and the dimensions of the PV panel fixed over the roof of a solar powered car is given below. Assuming efficiency of the PV panel to be 30% solar p.v 2.2 m (a) Find the area of PV panel fixed over the roof of the car? (b) Calculate the power of incident solar radiations? (e) Find the power out of the PV panel? 1.1m

College Physics

1st Edition

ISBN:9781938168000

Author:Paul Peter Urone, Roger Hinrichs

Publisher:Paul Peter Urone, Roger Hinrichs

Chapter24: Electromagnetic Waves

Section: Chapter Questions

Problem 29PE: Integrated Concepts (a) Calculate the rate in watts at which heat transfer through radiation occurs...

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The surface area of an adult human is about 1.8 m2. Suppose a person with a skin temperature of 34°C is standing with bare skin in a room where the air is 25°C but the walls are 17°C.a. There is a “dead-air” layer next to your skin that acts as insulation. If the dead-air layer is 5.0 mm thick, what is the person’s rate of heat loss by conduction?b. What is the person’s net radiation loss to the walls? The emissivity of skin is 0.97.c. Does conduction or radiation contribute more to the total rate of energy loss?d. If the person is metabolizing food at a rate of 155 W, does the person feel comfortable, chilly, or too warm?
Problem: Radiation Related The energy flux associated with solar radiation incident on the outer surface of the earth's atmosphere has been accurately measured and is known to be 1,368 W/m^2. The diameters of the sun and earth are 1.39 X 10^9 and 1.27 x 10^7 m, respectively, and the distance between the sun and the earth is 1.5 × 10^11 m. (a) What is the emissive power of the sun? (b) Approximating the sun's surface as black, what is its temperature? (c) At what wavelength is the spectral emissive power of the sun a maximum? (d) Assuming the earth's surface to be black and the sun to be the only source of energy for the earth, estimate the earth's surface temperature.
Estimate the total energy loss by radiation if a person’s head is uncovered for 13.3 min on a very cold, −15.0°C day, assuming he is bald, his skin temperature is 35.0°C, and that skin has an emissivity (in the infrared) of 97.0%. Assume that the man’s head is spherical, with a radius of 10.0 cm. The Stefan–Boltzmann constant is 5.670 × 10−8 W/ (m2·K4).
At what wavelength is the radiation emitted by the human body at its maximum? Assume a temperature of 37°C.
The radiant energy incident on the earth's surface on a sunny day is roughly 900 W/m2.Collecting and focusing sunlight and using the focused beam to heat a fluid is an old idea,and as the environmental costs of fossil-fuel combustion mount, solar heating becomes anincreasingly attractive alternative.Suppose a house is to be designed that will have a circulating forced-air central-heating unit,and solar energy is contemplated as a heat source (backed up with a conventional furnace tobe used on cloudy days). If air is to be fed at a rate of 1000 m3/min at 20°C and 1 atm, andthe air is to be heated to 55°C before being discharged into the living space, what is therequired area of the solar collector plates? Assume 30% of the radiant energy incident on theplates is used to heat the air.
(a) Calculate the power per square meter reaching Earth's upper atmosphere from the Sun. (Take the power output of the Sun to be 4.001026 W.) (b) Part of this is absorbed and reflected by the atmosphere, so that a maximum of 1.30 kW/m2 reaches Earth's surface. Calculate the area in km 2 of solar energy collectors needed to replace an electric power plant that generates 750 MW if the collectors convert an average of 2.00% of the maximum power into electricity. (This small conversion efficiency is due to the devices themselves, and the fact that the sun is directly overhead only briefly.) With the same assumptions, what area would be needed to meet the United States' energy needs (1.051020J) ? Australia's energy needs (5.41018J) ? China's energy needs (6.31019J) ? (These energy consumption values are from 2006.)
Integrated Concepts (a) Calculate the rate in watts at which heat transfer through radiation occurs (almost entirely in the infrared] from 1.0 m2of the Earth’s surface at night. Assume the emissivity is 0.90, the temperature of the Earth is 15°C, and that of outer space is 2.7 K. (b) Compare the intensity at this radiation with that coming to the Earth from the Sun during the day, which averages about 800 W/m2, only hall of which is absorbed. (c) What is the maximum magnetic field strength in the outgoing radiation, assuming it is a continuous wave?
In the chapter on fluid mechanics, Bernoulli's equation for the flow of incompressible fluids was explained in terms of changes affecting a small volume dV of fluid. Such volumes are a fundamental idea in the study of the flow of compressible fluids such as gases as well. For the equations of hydrodynamics to apply, the mean free path must be much less than the linear size of such a volume, adV1/3 . For air in the stratosphere at a temperature of 220 K and a pressure of 5.8 kPa, how big should a be for it to be 100 times the mean free path? Take the effective radius of air molecules to be 1.881011 m, which is roughly correct for N2.
Is your textbook the kind of idealized object (described in section on radiation laws) that absorbs all the radiation falling on it? Explain. How about the black sweater worn by one of your classmates?
Even when shut down after a period of normal use, a large commercial nuclear reactor transfers thermal energy at the rate of 150 MW by the radioactive decay of fission products. This heat transfer causes a rapid increase in temperature if the cooling system fails (1 watt = 1 joule/second or 1 W = 1 J/s and 1 MW = 1 megawatt). (a) Calculate the rate of temperature increase in degrees Celsius per second (C/s) if the mass of the is 1.60105 kg and it has an average specific heat of 0.3349 kJ/kg . C. (b) How long would it take to obtain a temperature increase of 2000 C, which could cause some metals holding the radioactive materials to melt? (The initial rate of temperature increase would be greater than that calculated here because the heat transfer is concentrated in a smaller mass. Later, however, the temperature increase would slow down because the 500,000-kg steel containment vessel would also begin to heat up.)
One energy concept is a cogeneration system of photovoltaic solar cells combined with a thermal capture of the waste heat absorbed for hot water in homes. Do a first law analysis of a 2 kWe system where the solar photovoltaics are collecting 50% of the incoming solar irradiance, and are 10% efficient in converting sunlight directly to electrical power. What is the thermal energy available?
The surface area of an adult human is about 1.8 m?. Suppose a person with a skin temperature of 34.0 °C is standing with bare skin in a room where the air is 25.0 °C but the walls are 17.0 °C. A. There is a "dead-air" layer next to your skin that acts as insulation. If the dead-air layer is 5.00 mm thick, what is the person's rate of heat loss by conduction? B. What is the person's net radiation loss to the walls? The emissivity of skin is 0.98. C. What is the net total loss rate due to conduction and radiation combined? D. If the person is metabolizing food to heat at a rate of 155 W, what is their net rate of gain or loss?