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Investigating the resistance of resistance wire

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Introduction

David Swiggs

Cand: 7355

Centre: 53611

Investigating the resistance of resistance wire

Problem:  “Investigate one of the factors that effects the resistance of resistance wire”

Normal wire is used for conducting electricity; the best wire is the one that gives out the same amount of electricity that was put in. The wire is made out of copper because it is a good conductor of electricity. Resistance wire is used in appliances like dimmer switches. You can control how much electricity out of the end of the wire.

    Current is the movement of electrons through a structure that conducts electricity. These electrons are said to be delocalised.

image10.png

                                                                                                           Metal ions in an       image00.png

                                                                                                           ordered lattice

                                                                                               Localised electron cloudsimage01.png

                                                                                         associated with one particularimage02.png

                                                                                          nucleus

                  Delocalised ‘mobile’ electrons

Delocalised electrons are the ones that move in metals when electricity is passed through them. An alloy is two or more metals chemically combined. Resistance wire is made from nichrome; it is an alloy of nickel and chromium. In alloys the delocalised electrons are either blocked or moped up.

Factors

The factors that I think will affect the resistance of resistance wire are

  • Length
  • Diameter
  • Temperature
  • Material
  • Condition of the wire

From the ‘physics for you’ textbook, page 254, I found out the following statements:

‘As the length increases, the resistance increases, as cross-sectional area increases, the resistance decreases, as temperature increases, the resistance of wire increases’.

I also believe that the material will alter the resistance but by how much is unpredictable.

Plan

  1. Make sure the equipment works.
...read more.

Middle

image04.pngimage05.png

                  Resistance

image06.png

                                                 Length

The length is directly proportional to the resistanceimage11.png

Preliminary work

Equipment

  • Power pack
  • Ammeter
  • Voltmeter
  • Ruler
  • Sticky tape
  • Eureka wire Ǿ 0.37
  • 6 wires

Using the set up on the pervious page.  I will switch the power pack on. Then I will touch the end of wire B along the eureka wire and take measurements at intervals of ten centimetres. I will read both meters and record the readings on a table. To make it a fair test I will be careful to keep the current, thickness and temperature all constant.

Length (cm)

V (volts)

I (current)

Resistance (Ω)

100

2.5

0.5

5.00

90

2.4

0.6

4.00

80

2.35

0.7

3.56

70

2.3

0.75

3.07

60

2.25

0.8

2.81

50

2.2

1

2.20

40

2.1

1.2

1.75

30

1.9

1.5

1.27

20

1.7

2

0.85

10

1.35

3.1

0.44

The temperature rose once the current was passed through it, which will cause the atoms in the wire to vibrate, and so obstruct the flow of electrons, so the resistance will increase creating an error. In my final experiment to make it fair I have to keep the temperature constant, I will accomplish this by adding a variable resistor to the keep current the same. Therefore if the current is the same the wire will not heat up.

Final Experimentimage12.png

I will perform this experiment the same as I did in my preliminary experiment except I have added a variable resistor to keep the current the same and the temperature constant.

...read more.

Conclusion

If I were to do the experiment again I would a more accurate method of measurement and take a much wider range of readings and more readings so that a more accurate average can be taken. I have also found out there is a much easier and reliable way to perform the experiment (shown below)

image14.png

In this experiment the resistance wire is used and set up in the same way in which a variable resistor is used. This would take a lot less time and the results would be a lot more accurate because nothing has to be adjusted you could just place the wire on wherever you need a reading.

     I would also take readings at 5cm intervals instead of 10cm. This would obviously be more accurate and reliable, but it would also tell if the rule resistance is proportional to length if true at 5cm intervals. Ultimately I would use a lot of different types of resistance wire to see if the rule were true for all materials.

...read more.

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