Practice Problems Heat Transfer Methods

Directions: On this worksheet you will investigate properties of the three heat transfer methods.

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Question 1  Which method of heat transfer involves actual particles circulating from one region to another?
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Question 2  Which heat transfer method can take place without a medium, that is, in a vacuum?
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Question 3  Newton's Law of Cooling allows us to calculate the rate at which the temperature difference between a hot object and the ambient room temperature changes with the passage of time. Tdiff = To e-kt. At time t = 0, the original temperature difference between a hot solid and the ambient room temperature is 62.6 ºC. If the temperature difference drops to half that value in 15.5 seconds, what is the value of the decay constant, k?
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Question 4  At what time will the temperature difference equal 13.8ºC?
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Question 5  An incandescent black body has a peak wavelength of 489 nm when its temperature is 5930 Kelvin. What would be the temperature of a second blackbody radiator that has a peak wavelength of 322.74 nm?
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Question 6  Compare the rate at which energy is given off by the second black body in Question #5 which has a peak wavelength of 322.74 nm to the first black body which has a peak wavelength of 489 nm.
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Question 7  If two other incandescent solids are at the same temperature, but one has a surface area that is 3 times greater, how would the radiant power of the larger black body compare to the rate at which energy is emitted by the smaller black body?
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Question 8  One end of a 62.6-cm copper rod (a = 385 W/mK) is placed in 100 grams of cold water at a temperature of 3.1 ºC. The other end is placed in the flame of a bunsen burner at a temperature of 924 ºC. If the rod has a radius of 0.3 cm, then what is the initial rate at which heat is conducted along the rod?
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Question 9  If a second copper rod has the same length as the rod in Question #8 but has a radius of 0.066 cm, how would the rate of conductivity be changed?
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Question 10  If a third copper rod has the same radius as the rod in Question #8, but a length of 83.88 cm, how would the rate of conductivity be changed?
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Question 11  A 350 watt immersion heater is used to heat a cup of water containing 183 grams of water and a piece of ice. The cup is made of styrofoam which is an insulator and does not give up or receive heat. If it takes 2.82 minutes for the heater to bring the contents of the cup from 0ºC to 65ºC, how much ice was originally present? Here are some constants: cice = 2093 J/kgºC, cwater=4186 J/kgºC, Lf = 334 kJ/kg