Carry out an investigation of the relationship between the length of a metallic conductor (eg Nichrome Wire) and its resistance

1
Carry out an investigation of the relationship
between the length of a metallic conductor (eg
Nichrome Wire) and its resistance
2
Introduction
3
Background research outlined and referenced

• Firstly I researched this topic in my science
  book. I found relevant information in my book
  about resistance, such as the fact that
  resistance is governed by the formula V IR
  and is measured in Ohms.
• Ohms can be measured using a multimeter
  (OCallaghan M., Reilly S., Seery A., Exploring
  Science 2003 p86-88)

4
Background research outlined and referenced

• Next I found a definition for Resistance on the
  internet
• A force that opposes the flow of an electrical
  current around a circuit, so that energy is
  required to push the charged particles around the
  circuit
• (http//www.sci-journal.org)

5
Background research outlined and referenced

• I found out from my Science Teacher that a
  metallic conductor is a wire, for example, copper
  wire

6
Investigation is stated as a problem statement

• During the investigation I intend to answer the
  following question
• How does the length of a wire affect its
  resistance

7
Preparation Planning
8
Identification of variables

• Independent Variable
• The LENGTH of the nichrome wire.
• Dependent Variable
• The RESISTANCE of the wire
• Fixed Variables
• TYPE of Wire
• SETTING on Multimeter
• THICKNESS of Wire

9
A Fair Test where appropriate is outlined

• To ensure a fair test, we ensure that the fixed
  variables remain the same.
• ie TYPE of wire
• THICKNESS of wire
• SETTING on multimeter
• This way, we are sure that when we change the
  length of the wire, this and this alone, will
  change its resistance.

10
Resource List Complete

• Length of wire
• Pliers
• Multimeter
• Meter Stick
• Safety Glasses
• Lab Coat
• Connecting wires
• Crocodile clips

11
Plan adequate to test the problem statement

• The problem statement states
• How does the length of wire affect its
  resistance.
• To plan for this, I must first do a trial run

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Trial Run

• Take a length of wire and connect it to the
  multimeter using crocodile clips.
• Then take another length and do the same.

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Issues I came across

• Do I start with 1 meter and cut off 10cm each
  timeyes
• How do I cut it off..the pliers wasnt sharp
  enough
• The ends of the wire was kinked..would this
  affect my results.yes (I asked the teacher)
• What settings do I have on the multimeter

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Procedure and Planning
15
Safety

• Do not handle multimeter with wet hands
• As this may give a shock
• Take care when using pliers to avoid accidental
  injury
• Wear safety goggles, as any wire when cut can
  recoil backwards and injure

16
Procedures Listed in Clear Logical order

• Gather all apparatus
• Put on protective clothing
• Set up apparatus as shown in the diagram
• Set multimeter to the Ohm setting. Insert one
  lead into the COM socket and the other into the
  K?mA socket. Ensure the claws are attached to the
  very end of the wire

17
Procedures Listed in Clear Logical order

• Ensure that the wire is fully extended without
  kinks or loops which would affect results
• Record this length of wire and its corresponding
  resistance. To start with we use 1 meter.
• Now remove the wire and cut off 10 cm ensuring
  the ends cut cleanly

18
Procedures Listed in Clear Logical order

• Record length and corresponding resistance.
• Repeat at 80 cm, 70 cm, 60 cm.10 cm
• Take another 1 meter length and get its
  resistance at the various length

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Recorded Data
Length / cm Resistance1 / ? Resistance1 / ? Total Resistance1 / ?
100 7.3 7.4 7.35
90 6.6 6.7 6.65
80 5.9 5.9 5.9
70 5.3 5.1 5.2
60 4.5 4.45 4.475
50 3.8 3.8 3.8
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Labelled Diagram
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Observations

• I did a trial run to get a feel for the
  experiment
• I did the experiment twice to get the average
• I made sure that the wire was not kinked or
  looped and that the ends were cut correctly.

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Observations

• I noted that the resistance of the wire was
  proportional to the length

23
Graph

• O
• Length / cm

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Calculations / Data Analysis
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Calculations accurate and clearly shown

• Data for Table
• (Resistance 1 2) / 2
• Eg (7.3 7.4) / 2 7.35O

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Relationship between variables discussed

• I found that the resistance of the wire was
  directly proportional to the length.
• With only two exceptions, I found that a decrease
  in length of 10 cm resulted in a decrease of
  0.7O in resistance

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Relationship tested over full range

• The full range was every 10 cm from 100 cm down
  to 10 cm
• This was 10 sets of information, taken twice and
  the average found.

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Comments
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Comments on the suitability of procedure

• We repeated the test three times to find the
  average results, but we disregarded the first set
  of results, as we cut too much off the wire and
  we found that the ends were cut poorly due to a
  blunt pliers.
• If we were to do this experiment again, we would
  ensure three good results

30
Comments on the suitability of procedure

• If repeating test I would also use thinner wire,
  to make it easier to cut.
• I would use sellotape to tie down the wire to
  make it easier to read.

31
Real Life implication

• Electrical appliances where you want to give out
  heat, should have a high resistance, whereas if
  you want to conduct electricity it should have a
  low resistance.

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Relationship between Findings and Problem
Statement

• The longer the wire, the more resistance there is.