Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Multiple-Choice Questions(Junior Science Level)

Energy Use at Home

Home Heating

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 1

You come into a cold room and switch on the space heater. Which statement is true during the time when the temperature in the room is rising?A. The power delivered by the heater is larger

than the heat lost from the room.B. The power delivered by the heater is smaller

than the heat lost from the room.C. The power delivered by the heater is the same

as the heat lost from the room.

Home Heating

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 1 Answer

You come into a cold room and switch on the space heater. Which statement is true during the time when the temperature in the room is rising?A. The power delivered by the heater is larger

than the heat lost from the room.B. The power delivered by the heater is smaller

than the heat lost from the room.C. The power delivered by the heater is the same

as the heat lost from the room.

Home Heating

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 2

On a cold, still day, you are trying to determine the energy balance of your home. Which of these assumptions of energy flow is unreasonable?

Home Heating

HouseHeat

generated inside house

C

(heat loss to cold air through conduction)A

Energy Flow In

(from sunshine)

B

Energy Flow In

(“fuel”)

D

(heat loss to the air through convection)

E

(heat loss to cold air through radiation)

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 2 Answer

On a cold, still day, you are trying to determine the energy balance of your home. Which of these assumptions of energy flow is unreasonable?

Home Heating

HouseHeat

generated inside house

C

(heat loss to cold air through conduction)A

Energy Flow In

(from sunshine)

B

Energy Flow In

(“fuel”)

D

(heat loss to the air through convection)

E

(heat loss to cold air through radiation)

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 2 Solution Home

Heating

The sun’s radiation energy will enter the house through the window. The furnace will heat up the house, as will many appliances within the house (lights, people). As the house warms up, heat will be lost to the air through radiation and convection, not conduction. This is because the heat is lost to a mobile fluid (the air), not a solid, even though the mobile fluid is still. If it were a windy day, it would be forced convection.

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 3

Suppose you are an astronaut in space, hard at work in your sealed spacesuit. The only way that you can transfer heat to the environment is by:

A. ConductionB. ConvectionC. RadiationD. Evaporation

Home Heating

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 3 Answer

Suppose you are an astronaut in space, hard at work in your sealed spacesuit. The only way that you can transfer heat to the environment is by:

A. Conduction

B. Convection

C. Radiation

D. Evaporation

Home Heating

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 3 Solution

In space there is no matter. Both conduction and convection require matter to transfer heat. Radiation as means of heat transfer does not require any medium and there is no exchange of mass.

Home Heating

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 4

A. Less than $ 25

B. $ 25

C. $ 50

D. $ 100

E. More than $ 100

Home Heating

A kWh in B.C. costs currently ~ 7.0 cents. The total energy consumption in a 1000 ft2 (~100m2) large apartment is approximately 200 MJ per day. If the apartment is heated electrically, what’s the energy cost each month?

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 4 Answer

A. Less than $ 25

B. $ 25

C. $ 50

D. $ 100

E. More than $ 100

Home Heating

A kWh in B.C. costs currently ~ 7.0 cents. The total energy consumption in a 1000 ft2 (~100m2) large apartment is approximately 200 MJ per day. If the apartment is heated electrically, what’s the energy cost each month?

Physics and Astronomy Outreach Program at the University of British ColumbiaPhysics and Astronomy Outreach Program at the University of British Columbia

Question 4 SolutionHome

Heating

kWh 1 J106.3 If 6 xkWh/day J/day 10200Then 6 x

kWh/day 65.55J106.3

kWh) 1(J/day)10200(

6

6

x

days 30kWh/day 65.55month oneIn

kWh 1666.67 :month onein cost energy total theSo

$166.67 $0.07/kWh kWh 1666.67