

U-values
Presentation
•
Physics
•
10th - 12th Grade
•
Easy
Andrew May
Used 3+ times
FREE Resource
12 Slides • 11 Questions
1
U-values

2
Open Ended
What factors might affect the rate at which thermal energy passes through a closed window? List as many as you can think of.
3
The rate of energy transfer depends on:
The temperature difference (inside-outside)
The area of the window
The thickness of the window
The thermal conductivity of the glass/air
4
Multiple Choice
A bigger temperature difference will cause the rate of energy transfer to
increase
decrease
stay the same
5
Multiple Choice
Energy transfer will increase if the window has a surface area that is
large
small
impossible to tell
6
Multiple Choice
Making a window thicker will
increase the rate of energy transfer
decrease the rate of energy transfer
make no difference
7
Multiple Choice
A window with high thermal conductivity will transfer energy
quickly
slowly
8
U-values
To simplify calculations, building materials are given a rating called a U-value.
The units of a U-value are W/(m2 oC)
9
Open Ended
Write out what
W/(m2 oC)
means in your own words, using a proper sentence.
10
W/(m2 oC)
This is the rate of energy transfer in watts (joules per second) for each square metre of window, and for each degree celcius temperature difference across it.
11
Can you see what factors have been incorporated into a U-value to make it simpler to calculate?
thickness & thermal conductivity
12
Open Ended
energy transfer rate = U-value * area * T difference
If a window has
a U-value of 2.8,
an area of 2m2,
and a temperature difference across the window of 10oC ,
what will be the rate of energy transfer across it?
Give your answer in watts to the nearest whole number.
13
2.8 * 2 * 10 = 56W
14
Multiple Choice
A cavity wall has a U-value of 1.7. What would be the energy transfer rate for a single outside wall that is 4m wide and 2m tall, if the temperature inside is 20oC and outside it is 5oC?
1360 W
272 W
204 W
56 W
15
16
17
18
What was the temperature of the hot metal plate?
give your answer in the next slide.
19
Multiple Choice
What was the temperature of the hot metal plate?
100 deg C
80 deg C
60 deg C
25 deg C
20
Which material is the best insulator?
give a reason for your answer in the next question.
21
Open Ended
Which material is the best insulator. Give a reason for your answer
22
The table gives information about four types of insulation that could be used for insulating the cavity walls of houses.
Which one of the types of insulation in the table would be the best to use for cavity wall insulation?
23
Multiple Choice
which one of the types of insulation in the table would be the best to use for cavity wall insulation?
felt wool
mineral wool
polyurethane foam
rock wool
U-values

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