1. M. Manser Invicta Grammar School GCSE PHYSICS MODULE P1: ENERGY FOR THE HOME Item P1a: Heating Houses At the start of this presentation, you will review heat loss by radiation. Then you will examine some thermograms showing where energy is lost from houses and some other objects.

2. M. Manser Invicta Grammar School Heat loss by radiation All warm objects radiate heat energy in the form of infrared waves. The higher the object’s temperature, the more IR waves it will emit. A dull, black object (when hot) will radiate its energy away very quickly. Whereas a hot object will retain its heat energy better if it has a silvery surface. IR waves are very similar to light waves, but they are invisible to the human eye. Special cameras must be used to obtain infrared images. The pictures are called “thermograms” since they show hot regions and cold regions very clearly.

3. M. Manser Invicta Grammar School Some thermograms Generally, we lose most of our heat from our heads. Look at the colour scale that was used to determine hot and cool areas. This technique is used in medicine to look for circulation problems.

4. M. Manser Invicta Grammar School Look carefully at the scale, this computer has used slightly different colours in their temperature scale. By carefully comparing the heat distribution patterns, a vet can spot potential problems. Can you? Heat is lost from the blood as it circulates. Cold spots suggest diminished blood flow in that area.

5. M. Manser Invicta Grammar School Thermogram of an aeroplane From which area is most heat being lost? Why would the body of the plane be designed in this way?

6. M. Manser Invicta Grammar School Thermogram of an elephant Which area is the coolest? An elephant’s ears are large and thin. The blood flowing through the veins, arteries and capillaries can be cooled easily. When the temperature of the environment rises, the elephant flaps its ears to cool the blood flowing through them. This then circulates through the rest of the body to cool the animal down.

7. M. Manser Invicta Grammar School Thermograms of houses This picture shows two houses. The one towards the back is a much older house. Which house is allowing more thermal energy losses? The older house is losing large amounts of heat through the walls, windows and the chimney!