7th grade energy

Question 1

Which kind of energy transfer is this: warmth from a campfire you are not touching?

• A. conduction
• B. convection
• C. radiation

Question 2

Heat transfer: which statement is NOT true?

• A. Convection cannot happen in solids.
• B. Dark, matt surfaces are good absorbers and emitters of infrared radiation.
• C. Air trapped in materials makes good insulation.
• D. Coats make heat.

Question 3

A games console with a power of 0.5 kW is used for 3 hours. How much energy does it transfer, in kWh?

Answer kWh

Question 4

Electricity costs 20c per kWh. How much does 5 kWh cost, in euro cents?

Answer 

Question 5

Why is a radiator usually placed low down near a wall?

• A. So it can conduct heat through the floor
• B. Warm air rises from it and sets up a convection current around the room
• C. Because cold air rises
• D. It works only near walls

Question 6

An electric heater rated at 1500 W runs for 90 minutes. Electricity costs 24¢ per kWh. What does it cost, in cents?

Answer 

Question 7

Which kind of energy transfer is this: your hand warming a cold metal rail?

• A. conduction
• B. convection
• C. radiation

Question 8

Heat transfer: which statement is NOT true?

• A. Convection cannot happen in solids.
• B. Coats make heat.
• C. Dark, matt surfaces are good absorbers and emitters of infrared radiation.
• D. Metals are good thermal conductors.

Question 9

A washing machine with a power of 0.5 kW is used for 3 hours. How much energy does it transfer, in kWh?

Answer kWh

Question 10

Electricity costs 20p per kWh. How much does 10 kWh cost, in pence?

Answer 

Question 11

Why is a radiator usually placed low down near a wall?

• A. Warm air rises from it and sets up a convection current around the room
• B. Because cold air rises
• C. It works only near walls
• D. So it can conduct heat through the floor

Question 12

An electric heater rated at 1000 W runs for 30 minutes. Electricity costs 30¢ per kWh. What does it cost, in cents?

Answer 

Question 13

Which kind of energy transfer is this: water circulating in a heated pan?

• A. conduction
• B. convection
• C. radiation

Question 14

Heat transfer: which statement is NOT true?

• A. Air trapped in materials makes good insulation.
• B. Dark, matt surfaces are good absorbers and emitters of infrared radiation.
• C. Cold flows into warm objects.
• D. Convection cannot happen in solids.

Question 15

An oven with a power of 3 kW is used for 5 hours. How much energy does it transfer, in kWh?

Answer kWh

Question 16

Electricity costs 15p per kWh. How much does 8 kWh cost, in pence?

Answer