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The Effects of Temperature on Resistance.

Extracts from this document...

Introduction

James O'Farrell        Page         5/2/2007

The Effects of Temperature on Resistance

The Effects of Temperature on Resistance

Aims

To investigate the effects of temperature on resistance.

Background Research

Apparatus

Diagram

The Variables

The Measured Variables

Accuracy

Data Range

Proposed Data Processing

Results

Raw Data

Processed Data

Graph of Processed Results

Analysis or Results

Planning

Background Research

Form background reading and research I have discovered that for most materials that conduct electricity there is some degree of variation of resistance with temperature. There is a set equation governing this change as follows;

Rθ= R0(1+αθ) = R0 + αR0θ

Where

Rθ= Resistance at Temperature θ

R0         = Resistance at 0°C

α         = The temperature coefficient of resistance.

As we will see after we have done the experiment the temperature coefficient will turn out to be negative as I am sing a N.T.C. Thermistor

Apparatus

• Negative temperature coefficient thermistor.
• Voltage meter (V)
• Ammeter (A)
• Power Pack (Low voltage DC)
• Freezer
• Heater
• Beaker
• Thermometer

The Variables

In this section I will look at all the possible variables and decide which ones should be varied in order to obtain results showing the effect of temperature on resistance.

Middle

16

1.94

0.216

1.96

0.216

34

1.66

0.308

1.66

0.309

39

1.48

0.307

1.48

0.310

48

1.35

0.342

1.35

0.346

57

1.21

0.372

1.22

0.371

66

1.15

0.454

1.17

0.447

77

1.01

0.506

1.02

0.489

83

0.90

0.474

0.88

0.465

Processed Data

 Temp Set1 Resistance = Set 2 Resistance = Average +/- 0.5°C Voltage (V) Current (A) V/I (Ω) Voltage (V)

Conclusion

We can work out the temperature coefficient at using the equation and taking an average of all the results.

Rθ= R0(1+αθ) = R0 + αR0θ

 Temp Average Temperature R (Ω) Coefficient 0 17.3 ∞ 11 10.8 -0.0339 16 9 -0.0298 34 5.4 -0.0202 39 4.8 -0.0185 48 3.9 -0.0161 57 3.3 -0.0142 66 2.6 -0.0129 77 2 -0.0115 83 1.9 -0.0107

As we can see from the graph above the temperature coefficient is indeed negative, but it is not a straight line and therefore not constant. This can be explained by the fact that the thermistor itself dose not have a constant rate of change but instead it has a range depending on the temperature.

One conclusion that can be drawn from the data that we have obtained it that there is a distinct change in resistance wit temperature. This can be seen in the first graph, as the temperature rises the resistance falls (NTC).

In further investigation I would like to investigate resistance change and temperature for different components. Also I would like to look at the heating effect on resistors and other components as I think this ma have had some affect on the results.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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