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Investigating how the length of a wire affects its resistance.

Extracts from this document...

Introduction

Wednesday 27th 2001F.Nazmin Hussain 10.E

Investigating How The Length Of A Wire Affects Its Resistance

The factors in this investigation are:

The material used for the wire, as some materials are better conductors of electricity than others so more electrons will pass through good conductors.

Cross-sectional area as the thickness of the wire increases the resistance decreases, for example if the wire is thicker more electrons will be able to pass through and if the wire is thinner fewer electrons will be able to pass through, thus a higher resistance.

Length of the wire as the length increases the resistance increases this is because the electrons have further to travel thus there is more resistance.

Temperature of the wire as the temperature increases the resistance decreases, for example if the wire is hot there will be a lower resistance and if cold there will be a higher resistance.

I am going to investigate whether changing the length of a wire affects the resistance (of the wire).  

Planning:

The independent variable I have chosen to change is the length of the wire.

The controlled variables are the materials used for the wire, the cross-sectional area and the temperature of the wire.

The dependant variables are the potential difference and current.

I will work safely by using equipment properly by putting equipment away after use and by handling the electrical equipment and the sharp, thin wires carefully. Therefore the equipment is kept well away form the edge of the bench and that the electrical equipment is well supervised.  

I will make sure that scrap pieces of wire are thrown away after use.  

I will make sure that the electrical equipment is kept well away from liquids and solutions, such as water in nearby taps.  

...read more.

Middle

Preliminary Results

Length Of Wire (mm):

Voltage (V):

Current (A):

Resistance ():

0

0

0.5

0

100

0.01

0.5

0.02

200

0.03

0.5

0.06

300

0.05

0.5

0.1

400

0.06

0.5

0.12

500

0.08

0.5

0.16

600

0.09

0.5

0.18

700

0.11

0.5

0.22

800

0.12

0.5

0.24

900

0.14

0.5

0.28

1000

0.15

0.5

0.3

Therefore this information supports my prediction that the longer the length of wire the higher the resistance.

Obtaining Evidence:

The variables I kept the same are:

The same material used for the wire,

The same cross-sectional area of wire,

And the same temperature of the wire.

The potential difference from the power pack: 2V.

The current, which measured the rheostat, was kept at: 0.5A.

The lengths of the copper wire:

0 mm,

100 mm,

200 mm,

300 mm,

400 mm,

500 mm,

600 mm,

700 mm,

800 mm,

900 mm,

1000 mm.

The readings from the voltmeter and the ammeter were measured to two decimal places.

Test One:

Length Of Wire (mm):

Voltage (V):

Current (A):

0

0

0.5

100

0.01

0.5

200

0.03

0.5

300

0.05

0.5

400

0.06

0.5

500

0.08

0.5

600

0.09

0.5

700

0.11

0.5

800

0.12

0.5

900

0.14

0.5

1000

0.15

0.5

Test Two:

Length Of Wire (mm):

Voltage (V):

Current (A):

0

0

0.5

100

0.01

0.5

200

0.03

0.5

300

0.04

0.5

400

0.06

0.5

500

0.08

0.5

600

0.09

0.5

700

0.11

0.5

800

0.13

0.5

900

0.14

0.5

1000

0.15

0.5

Test Three:

Length Of Wire (mm):

Voltage (V):

Current (A):

0

0

0.5

100

0.02

0.5

200

0.03

0.5

300

0.05

0.5

400

0.06

0.5

500

0.08

0.5

600

0.09

0.5

700

0.11

0.5

800

0.12

0.5

900

0.14

0.5

1000

0.15

0.5

Test Four:

Length Of Wire (mm):

Voltage (V):

Current (A):

0

0

0.5

100

0.02

0.5

200

0.04

0.5

300

0.06

0.5

400

0.08

0.5

500

0.09

0.5

600

0.1

0.5

700

0.11

0.5

800

0.12

0.5

900

0.13

0.5

1000

0.15

0.5

...read more.

Conclusion

The ranges between my results were small and fairly close on the tables, which indicated accuracy. Although when I converted my results into a line graph I found that six out of the eleven results were anomalous results, which was probably due to human error and probably due to defaults in the meters, as they were battery powered. Also the sensitivity of the meters as they were not very sensitive and therefore my results were affected by this.

Even though there were anomalous results they were fairly close to the line of best fit as they were either just above or just below the line of best fit. Therefore the results were quite accurate and so I felt that I did not need to repeat any of the results and that I did not need to record any more results, as the results still justified my prediction.

Furthermore I could have changed the line of best fit so that more of the results fitted in with the line.

The improvements I could have made to make the results more accurate would be to use a much more sensitive ammeter and voltmeter, so I could have recorded my results to three or four decimal places, which would have made my results more accurate.

Moreover I could have had shorter length ranges to show better accurate results, to see how a small increase in length affected the resistance compared to a large increase in length. So I could have use the range of lengths from zero millimetres to twenty millimetres to 40 millimetres and so on rather than the range I chose, which was zero millimetres to 100 millimetres to 2000 millimetres and so on, which therefore would have affected the results (resistance).

As a result this would have shown the pattern better, clearer and easier to point out and it would have improved the line of best fit.

...read more.

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