Deck 3: Heat

Question 1

Which of the following situations would be allowed by the second law of thermodynamics?

A) running of a heat engine using temperature differences in the oceans
B) converting 100 joules of heat energy into 100 joules of work
C) passage of heat from the freezer into the refrigerator section
D) the reduction of waste heat from a power plant to zero with better technology

Answer 1

A

Question 2

When ice crystals form in the clouds, ________.

A) heat energy is released
B) the atmosphere becomes colder
C) phase change from solid to liquid occurs
D) the thermal mass of the atmosphere increases

Answer 2

A

Question 3

Heat energy will spontaneously always flow in the direction of ________.

A) a higher temperature
B) a lower temperature
C) up, since heat rises
D) a smaller heat capacity

Answer 3

B

Question 4

An object with a high specific heat will ________.

A) lose its heat very fast
B) decrease in temperature quite fast if removed from the heat source
C) take considerably more heat to raise its temperature
D) always be water

Question 5

The cooling effect in a refrigerator is produced by _____.

A) the electric motor which essentially converts electricity into heat
B) compression of the refrigeration gas into a liquid
C) liquefying the refrigeration gas
D) vaporization of the refrigeration liquid
E) proper insulation

Question 6

Since the rate of heat transfer by conduction is proportional to the $\Delta$ T, what percent savings in your heating bill would you expect if you turned the thermostat down from 75 $\degree$ to 65 $\degree$ , and the outside temperature is 25 $\degree$ F?

A) 10%
B) 20%
C) 30%
D) 40%
E) 50%

Question 7

Materials A, B, and C have R values of 1, 4, and 8 ft2- $\degree$ F-hr/Btu, respectively. If the rate of heat transfer through material A alone is 20 Btu/hr, then the rate of heat transfer through the combination of A, B and C is _____.

A) 1.5
B) 2.5
C) 4.0
D) 7.0
E) 80 Btu/hr

Question 8

What color would you select for a container that will hold ice cubes such that the ice is preserved the longest?

A) white
B) black
C) green
D) color doesn't matter

Question 9

For a furnace to provide 50,000 Btu/hr of thermal energy to a living space, what should the rate of heat supplied by the fuel if the furnace efficiency is 75%?

A) 25,000
B) 37,000
C) 50,000
D) 67,000
E) 125,000 Btu/hr

Question 10

Infiltration in a house will ________.

A) increase on windy days
B) raise the heating load by about 10%
C) reduce the number of air changes
D) be increased by caulking around windows

Question 11

The temperature on an Oswego, New York "warm" spring day has a maximum of 64 $\degree$ F and a minimum of 30 $\degree$ F. What is the number of heating degree days?

A) 18
B)30
C) 34
D) 47
E) 64

Question 12

The R-value of a piece of material goes up if the material is

A) thicker
B) a better conductor
C) covering a larger area
D) thinner

Question 13

A heat pump will have an efficiency (heat out to electrical in) of about ________.

A) 35%
B) 50%
C) 75%
D) 100%
E) 200%

Question 14

Your feet feel warmer on a rug than on a tile floor because the rug

A) is usually warmer than the tile
B) is a better insulator than tile
C) has more internal energy than tile for the same mass
D) all of these

Question 15

The "R-value" of material is not related to its ________.

A) composition
B) area
C) thickness
D) resistance to heat flow

Question 16

If the R-value of a wall is 10 ft2-˚F-hr/Btu, then the rate of heat transfer through a 2 ft - 3 ft section of wall, with $\Delta$ T = 50 $\degree$ F, will be:

A) 10
B) 30
C) 500
D) 3000
E) 10,000 Btu/hr

Question 17

Running a clothes dryer for 90 minutes at 800 Watts will cost about ______ cents if the cost of electricity is 7 cents per kWh:
A ) 4
B) 10
C) 24
D) 50
E) 120

Question 18

Heat is ________.

A) a measure of the average kinetic energy of molecules in an object
B) a property of an object
C) the energy transferred between bodies due to a temperature difference
D) the specific heat of an object

Question 19

At a restaurant you are served coffee before you are ready to drink it. In order that the coffee be the hottest when you are ready for it, when would it be best to add cream (at room temperature) to it?

A) when you are ready to drink it
B) right when you are served the coffee
C) it doesn't matter, as the final temperature will be the same

Question 20

The predominant method of heat transfer to a cold drink held in an evacuated bottle (a thermos)
Is by ________.

A) conduction
B) convection
C) radiation

Question 21

Hot water in a _______ can will cool off faster than hot water in any other color can.

A) white
B) red
C) black
D) silver

Question 22

The greatest percentage of heat loss from an average house with 6-inches of fiberglass in the walls, 4-inches in the floor, 9-inches in the roof, and double pane windows, comes from the ________.

A) roof
B) walls
C) floor
D) windows

Question 23

For a cube-shaped room, 10 ft on a side, what will be the rate of heat loss if the R-value is 4 ft2- $\degree$ F-hr/Btu for each side and the $\Delta$ T is 50 F?

A) 800
B) 1200
C) 5000
D) 7500
E) 12,000 Btu/hr

Question 24

The primary method by which the water in a pot is heated is by ________.

A) conduction
B) convection
C) radiation
D) evaporation
E) condensation

Question 25

The most cost effective way to reduce heat loss from a window is ________.

A) add a storm window
B) install a triple pane window
C) weatherstrip around the outside perimeter of the window
D) install a thermal drape

Question 26

The greatest source of heat loss in a new home is from the ________.

A) roof
B) walls
C) floor
D) windows
E) infiltration

Question 27

As a liquid changes into a vapor ________.

A) heat energy is absorbed
B) heat energy is given off
C) the temperature of the liquid rises substantially
D) the specific heat maintains the temperature

Question 28

A heat engine ________.

A) converts work into heat energy
B) needs a temperature difference to be able to work
C) can be 100% efficient in the absence of friction
D) needs electricity to be able to run

Question 29

How much heat does it take to increase the temperature of 5 lbs of water by 20 $\degree$ F?

A) 4
B) 25
C) 100
D) 800 Btu.

Question 30

Coffee will cool faster when put into a saucer due to

A) conduction
B) evaporation
C) condensation
D) a and b
E) b and c

Question 31

Infiltration can be reduced primarily by ________.

A) insulation
B) double pane windows
C) weatherstripping
D) lowering the thermostat
E) furnace maintenance

Question 32

The flow of heat in a cold soft drink will be from ______.

A) the drink to the ice cubes
B) the drink to the outside air
C) the drink to the glass
D) the ice cubes to the drink

Question 33

The maximum efficiency of a heat engine operating between 2 $\degree$ C and 200 $\degree$ C will
Be about ________.

A) 10%
B) 40%
C) 60%
D) 90%
E) 100%