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Investigate how electrical resistance varies with different lengths of wire.

Extracts from this document...

Introduction

Kirsty Skinner 10/6

AT1-Electricity

Aim

To investigate how electrical resistance varies with different lengths of wire.

Hypothesis

I think that when the length of wire is increased, the resistance increases aswell.

In a piece of wire the atoms are arranged in a regular pattern called a lattice. The positive charges within an atom are concentrated in its nucleus and are unable to move, but the negative charges re the electrons, which are quite a distance away from the positive nucleus and are continually moving. Some of the outer electrons are able to drift from atom to atom. If a cell is connected across the wire more of the electrons will flow towards the positive terminal. This flow of charge creates an electrical current.

As the electrons in an electric current move around a circuit they bump into the atoms in the wire through which they pass. They collide with the atoms in the wire, which vibrate more quickly. We call this resistance. If the resistance of the wire is high, this means that the electrical current that is flowing is slowing down because of the resistance in the wire. If the voltage is high and the current is high, the wire increases in temperature, which causes yet more resistance in the wire.  

...read more.

Middle

1

40

0.18

0.1

1.8

1.825

2

0.37

0.2

1.85

1

60

0.26

0.1

2.6

2.6

2

0.52

0.2

2.6

1

80

0.34

0.1

3.4

3.45

2

0.7

0.2

3.5

1

100

0.43

0.1

4.3

4.35

2

0.88

0.2

4.4

1

120

0.54

0.1

5.4

5.425

2

1.09

0.2

5.45

Diagram 2

Method 2

  1. Set up apparatus as in the diagram.
  2. Using just the multi-meter, and the wires, measure the resistance through them. Then take away that resistance from the end measurement.
  3. Then use the 120cm of wire as the resistor.
  4. Turn on the multi-meter to ohms.
  5. Read off the resistance off the multi-meter, which calculates the resistance automatically. Put the reading into the results table.
...read more.

Conclusion

If I were to do the experiment again I would change the way we measured the wire.  I would attach the clip at the start, then measure the wire, and then attach the second clip so I would have the correct measurement of wire.

I can say that the conclusions I have got from the results are fairly safe.  My results support the prediction over the range investigated. It would be better to have more readings, say increasing by 5cm instead of 20cm to get more readings. By doing this I would get a better range of results and more points on my graph.

Overall I think my measurements were fairly accurate. From my graphs I can see the multi-meter test was more accurate because only 3 out of the 5 points were slightly out of the line.  I think I had these anomalies in my results because of the problems I had.

As before I explained that the first method wasn’t very accurate because I didn’t always get the exact measurements I wanted to work out the resistance so therefore my 2nd experiment had slightly different results, because of the different equipment I used, like the voltmeter and the ammeter, and then substituted them with an multimeter to produce a better, more accurate set of results.

As an alternative investigation I could look at how wires of different cross-sections, affect resistance.

...read more.

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