This Physics quiz is called 'Physics - Rate of Heat Transfer' and it has been written by teachers to help you if you are studying the subject at senior high school. Playing educational quizzes is one of the most efficienct ways to learn if you are in the 11th or 12th grade - aged 16 to 18.
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Heat is thermal energy and can be transferred from one location to another by conduction through solids, convection in fluids and as heat rays (thermal radiation). Conduction and convection involve the movement of particles but thermal radiation involves the electromagnetic waves known as infrared. These travel at the same speed as other electromagnetic radiation - the speed of light. This makes radiation the fastest way for heat to move from one place to another. It is so fast that it only takes just over 8 minutes for heat to reach the Earth from the Sun, about 150,000,000 km away!
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Conduction is how thermal energy is transferred through solids and the speed at which this happens varies. It is fastest in metals, which are good conductors of heat, and we can use them to increase the rate of heat transfer. Materials that do not allow heat conduction to happen quickly are called insulators. These are things like plastics, wood and materials that contain trapped air or other gasses. We can use insulators to decrease the rate of heat transfer.
Convection occurs in fluids and is the reason that hot air rises. A fluid is a liquid or gas. An area of a fluid that is warmer than surrounding areas is less dense and it rises. Cooler fluid then moves in to take its place. If the heating continues, the cooler fluid soon warms up and rises away from the heat source setting up a convection current. When you boil something in a pan, convection is the process that spreads the heat through the liquid.
Finding ways to increase and decrease the rate of thermal energy transfer is important in many applications. A scientist working in the Antarctic or a mountaineer climbing Everest both need clothing that slows down how fast that heat is transferred away from their bodies. Designers of LED lighting systems and computers on the other hand, need to find ways of increasing the rate of heat transfer to cool down the two devices.
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1.
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Which of the following would be the worst conductor of heat? |
|
| [ ] |
Copper |
| [ ] |
Wood |
| [ ] |
Aluminium |
| [ ] |
Brass |
|
|
|
2.
|
Which way does thermal energy travel? |
|
| [ ] |
From hotter to cooler |
| [ ] |
From cooler to hotter |
| [ ] |
From a conductor of heat to a non conductor |
| [ ] |
It varies depending on the situation |
|
|
|
3.
|
Which of the following features of a thermos bottle is designed to reduce the rate of heat transfer by radiation? |
|
| [ ] |
The vacuum |
| [ ] |
Cork base |
| [ ] |
The lid |
| [ ] |
Silvering the side walls |
|
|
|
4.
|
Which of the features of a thermos bottle is designed to slow down the rate of heat transfer by reducing both conduction and convection? |
|
| [ ] |
The vacuum |
| [ ] |
Cork base |
| [ ] |
The lid |
| [ ] |
Silvering the side walls |
|
|
|
5.
|
The smallest fox in the world, the fennec fox, lives in the Sahara desert. It has very large ears. How do its ears help it to keep cool? |
|
| [ ] |
They can be flapped backwards and forwards creating a cool breeze over the fox |
| [ ] |
The fox can twist and bend its ears to shade itself from the Sun |
| [ ] |
They have a large surface area |
| [ ] |
They don't help at all |
|
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6.
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A cool box is used to keep food cooler than the surroundings. They are often used to carry chilled or frozen food home from a supermarket or to keep food fresh at a picnic. Which of the following materials would be suitable to make the walls of a cool box? |
|
| [ ] |
Aluminum alloy |
| [ ] |
Thin plastic |
| [ ] |
Thick plastic |
| [ ] |
Polyurethane foam (a type of plastic that contains air bubbles) |
|
|
|
7.
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18,000 J of energy was transferred from an electric heater to a 2kg block of steel. The temperature increased by 18oC. Based on these figures, what is the specific heat capacity of the steel? |
|
| [ ] |
500 J/kg |
| [ ] |
3,600 J/kgoC |
| [ ] |
500 J/kgoC |
| [ ] |
3,600 W/kg |
|
|
|
8.
|
If 18,000 J of energy was transferred from an electric heater over the course of 2 minutes, what is the rate that heat was transferred? |
|
| [ ] |
150 J/s |
| [ ] |
150 W/s |
| [ ] |
9,000 J/s |
| [ ] |
9,000 W/s |
|
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9.
|
LEDs are low energy alternatives to conventional light bulbs but they still generate a lot of heat when they are switched on. They need to be attached to a heat sink to keep them cool. Which of the following would make a good heat sink for an LED? |
|
| [ ] |
A solid block of plastic |
| [ ] |
A solid block of metal |
| [ ] |
A block of polystyrene foam |
| [ ] |
A metal plate with fins |
|
|
|
10.
|
A group of students carried out an investigation into the rate at which different foods cool down. They measured the temperature of each food at 30 second intervals until the food had cooled from 80oC to room temperature. They then drew graphs of the results. In each case, the graph was the same shape. Which of the following describes the shape of their graphs? |
|
| [ ] |
A linear graph with a negative gradient |
| [ ] |
A lineear graph with a positive gradient |
| [ ] |
A curved line graph with a negative gradient that is steeper at higher temperatures |
| [ ] |
A curved line graph with a positive gradient that was steeper at lower temperatures |
|
|
|
1.
|
Which of the following would be the worst conductor of heat? |
|
| [ ] |
Copper |
| [x] |
Wood |
| [ ] |
Aluminium |
| [ ] |
Brass |
|
|
|
2.
|
Which way does thermal energy travel? |
|
| [x] |
From hotter to cooler |
| [ ] |
From cooler to hotter |
| [ ] |
From a conductor of heat to a non conductor |
| [ ] |
It varies depending on the situation |
|
|
|
3.
|
Which of the following features of a thermos bottle is designed to reduce the rate of heat transfer by radiation? |
|
| [ ] |
The vacuum |
| [ ] |
Cork base |
| [ ] |
The lid |
| [x] |
Silvering the side walls |
|
|
|
4.
|
Which of the features of a thermos bottle is designed to slow down the rate of heat transfer by reducing both conduction and convection? |
|
| [x] |
The vacuum |
| [ ] |
Cork base |
| [ ] |
The lid |
| [ ] |
Silvering the side walls |
|
|
|
5.
|
The smallest fox in the world, the fennec fox, lives in the Sahara desert. It has very large ears. How do its ears help it to keep cool? |
|
| [ ] |
They can be flapped backwards and forwards creating a cool breeze over the fox |
| [ ] |
The fox can twist and bend its ears to shade itself from the Sun |
| [x] |
They have a large surface area |
| [ ] |
They don't help at all |
|
|
|
6.
|
A cool box is used to keep food cooler than the surroundings. They are often used to carry chilled or frozen food home from a supermarket or to keep food fresh at a picnic. Which of the following materials would be suitable to make the walls of a cool box? |
|
| [ ] |
Aluminum alloy |
| [ ] |
Thin plastic |
| [ ] |
Thick plastic |
| [x] |
Polyurethane foam (a type of plastic that contains air bubbles) |
|
|
|
7.
|
18,000 J of energy was transferred from an electric heater to a 2kg block of steel. The temperature increased by 18oC. Based on these figures, what is the specific heat capacity of the steel? |
|
| [ ] |
500 J/kg |
| [ ] |
3,600 J/kgoC |
| [x] |
500 J/kgoC |
| [ ] |
3,600 W/kg |
|
|
|
8.
|
If 18,000 J of energy was transferred from an electric heater over the course of 2 minutes, what is the rate that heat was transferred? |
|
| [x] |
150 J/s |
| [ ] |
150 W/s |
| [ ] |
9,000 J/s |
| [ ] |
9,000 W/s |
|
|
|
9.
|
LEDs are low energy alternatives to conventional light bulbs but they still generate a lot of heat when they are switched on. They need to be attached to a heat sink to keep them cool. Which of the following would make a good heat sink for an LED? |
|
| [ ] |
A solid block of plastic |
| [ ] |
A solid block of metal |
| [ ] |
A block of polystyrene foam |
| [x] |
A metal plate with fins |
|
|
|
10.
|
A group of students carried out an investigation into the rate at which different foods cool down. They measured the temperature of each food at 30 second intervals until the food had cooled from 80oC to room temperature. They then drew graphs of the results. In each case, the graph was the same shape. Which of the following describes the shape of their graphs? |
|
| [ ] |
A linear graph with a negative gradient |
| [ ] |
A lineear graph with a positive gradient |
| [x] |
A curved line graph with a negative gradient that is steeper at higher temperatures |
| [ ] |
A curved line graph with a positive gradient that was steeper at lower temperatures |
|
|
