Worksheet 27 - Iowa State University

Phys 221 SI Worksheet:
Supplemental Instruction
Iowa State University
Phys 221
1. What are the three types of heat transfer? Explain each.
2. What is the formula describing the heat transfer for conduction? What is k?
3. What does the above equation mean conceptually about conduction?
4. Consider a hot object and a cold object connected by a solid rod. For each of the
following questions, in which scenario does heat transfer faster?
a) (case 1) T_H=400k, T_C=100k (case 2) T_H=400k, T_C=200k.
In both cases the rods are made of same material, are of the same length, and area.
b) (case1) rod is thicker and shorter (case 2) rod is thinner and longer
c) (case 1) the material of the rod has a higher thermal conductivity (case 2) the
material of the rod has a lower thermal conductivity
d) (case 1) rod has twice the area and is twice as long as (case 2)
5. If it is 20 degrees C inside and 0 degrees C outside, what is the heat flow through a glass
window of area 0.3 square meters and thickness 0.5cm? (thermal conductivity of glass is
about 1 W/mK)
6. Now consider the same problem but with a double pane window with a .5cm gap of air
between the panes? (thermal conductivity of air is .024W/mK)
7. What is the equation for the rate of heat transfer for radiation?
8. What does the above equation tell you about radiation?
9. What is e? What is σ?
10. What is the rate of heat loss of a black body with area of 1.5m^2, and a temperature of
100 degrees Celsius in a 0 degree Celsius room?
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