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# Conductivity or thermal conductivity is a measure of how good a conductor a material is. The rate of heat energy transfer through an object depends on the conductivity of the material and the temperature gradient.

Extracts from this document...

Introduction

Physics: Heat loss

Aim:

## Prediction

I predict that whenever there is a temperature difference , ehat energy will be transferred by conduction, convection or radiation fro the hotter to the cooler place. This increases the internal enrgy , which is the sum of the kinetic energy and the molecular potential energy of each molecule in an object, of the cooler atoms raising the temperature , and dreases the energy of the hotter atoms , lowering theirs. It continues until the temperature is the same across the region.

Conductivity or thermal conductivity is a measure of how good a conductor a material is. The rate of heat energy transfer through an object depends on the conductivity of the material and the temperature gradient.

Temperature = t2 -t

t1, t2+ temps at point 1 and 2

X=distance

This is the temperature change with distance along the material . The higher the conductivity and the steeper the gradient, the faster the energy transfer.

## Heat transfer to polystyrene cup

Convection is a way in which heat energy is transferred in liquids and gases. If a liquid or a gas is heated it expands, becomes less dense and rises. Cooler, denser liquid or gas then sinks to take its place. Thus convection current is set up.

### Coastal breezes used to explain convection currents

We use leslies cube in my preliminary work to measure radiation, radiation is a way

Middle

22.5 degrees

17.5 degrees

50 degrees and above

8.0 degrees

Average

17.25 degrees

10.0 degrees

Average

10.5 degrees

10 degrees

10.0 degrees

16.5 degrees

11 degrees

30 degrees and above

8.0 degrees

Average

7.33 degrees

5.5 degrees

Average

5.5 degrees

11.0 degrees

5.0 degrees

3.0 degrees

6.0 degrees

From this chart you can see that without the cardboard lid the results atre very random and this means that the heat is able to fluctuate greatly as you can tell from my results. I have therefore decided to have a lid on the cup as the results with the lid on seem a lot more constant and the heat isn’t allowed to fluctuate as much.

I suspect that I will find that heat energy will be lost mostly conductivity and convection rather than radiation as I have tried to reduce the effects of this to as little as possible . For my acual test I will change the integers at which heat is lost from e.g. instead of going 70 degrees and above to 50 degrees and above I will try to have exactly 70 degrees and exactly 65degrees, I will then be able to draw more accurate results from this.

## Equipment needed

. Polystyrene cup        . Kettle

. Thermometer                               . Stop watch

. Cardboard lid                               . Measuring cylinder

## How to set up the experiment

The experiment will be carried out in the following way:

1. Set apparatus uo as shown above.
2. Tap water will be put into a kettle to boil
3. It will then be put into a 100ml measuring cylinder to measure the amount of water
4. Pour water into a polystyrene cup, put lid on and take the temperature

Conclusion

1.0

1.0

1.0

55-50

3.0

4.0

3.5

50-45

2.0

3.0

2.5

45-40

2.5

2.0

2.25

40-30

1.5

0.0

0.75

This shows that my results were fairly constant and shows that my experiment was fair and therefore was a success.

##### Evaluation

As all of the pairs of my results were close I know that my experiment gave reproducible results. This shows that my experiment was a success and that my results were of a good quality. I do not believe I have any anomonlous results which shows to me that again my experiment was accurate. My line of best shape goes through all the results , this tells me that I have high quality results and a  good experiment.

I could improve my experiment if I was to do it again by using more viscous liquids which could give me an insight into how heat is lost in other liquids. I could also alternate the environment in which it is done in to see how it is effected by external as well as internal heat.

As an extension to this experiment I could use DL + as an electronic temperature measurment device would be more accurate. This would also be good because it can be set to take temperatures hundreds of times per second. This would give me a better curve of temperature vs time and would also allow a finer discrimibnation to take place. Another way in which I could extend the experiment could be to do it oppositly and determine how much energy is needed to maintain the temperature. To achieve this I would need new equipment such as electronics heating , a thermostadt and a joule meter. I could also work out the energy by doing the calculation below.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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