Question
Which change will cause a decrease in the rate of radiation emitted by an object?
A changing the surface colour from white to black
B changing the surface texture from dull to shiny
C increasing the surface temperature
D increasing the surface area
Answer/Explanation
Ans: B
Question
Some hot water is sealed inside a metal can. The can is in a vacuum in outer space. The hot
water slowly cools down.
How does the thermal energy escape into space?
by conduction then convection
by conduction then radiation
by evaporation then convection
by evaporation then radiation
Answer/Explanation
Ans: B
Question
The diagram shows a refrigerator.
The cooling unit is placed at the top. The cooling unit cools the air near it.
What happens to the density of the air as it cools, and how does it move?
| density of the air | movement of the air |
A | decreases | moves down |
B | decreases | stays at the top |
C | increases | moves down |
D | increases | stays at the top |
Answer/Explanation
Ans: C
Question
A boy sits near a campfire. He pokes the fire with an iron bar. His hand becomes hot.
In which ways does thermal energy (heat) from the fire reach his hand?
A conduction and convection only
B conduction and radiation only
C convection and radiation only
D conduction, convection and radiation
Answer/Explanation
Ans: B
Question
A man goes into a cold room and switches on a heater. The man then stands one metre away
from the heater. He feels warmer almost immediately.
How is thermal energy transferred from the heater to the man so quickly?
A. by conduction, convection and radiation
B. by conduction only
C. by convection only
D. by radiation only
Answer/Explanation
Ans: D