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Find out if there is a relationship between the current and the length of wire.

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Introduction

GCSE Physics Coursework

An investigation to find out how the current changes as the length of the wire changes.

AIM: To find out if there is a relationship between the current and the length of wire.

Planning

P2a. Safety

        Before we can go ahead with the experiment it is vital that we check that everything in the experiment is safe. A safety check would include checking that there are:

image01.png No loose connections

image01.png No sharp wires

image01.png No exposed wires

image01.png Steady surface

image01.png No water around

image01.png No power when experiment is not taking place

It is important that we keep these things safe, as it could interrupt the readings or even cause us to have no readings at all.

P4a. Fair test

                I need to keep the experiment as fair as possible.

Things I must keep constant:

image01.png We must keep the voltage constant if we use the battery a lot it will get weaker and this will change the current and give false results.

image01.png It is important that we use the same wire through the experiment because of different levels of resistance. This would also affect the final results. We will be using constantan wires through the experiment.

A thing I am going to vary:

image01.png

...read more.

Middle

        Varying cross sectional area of the wire

P6b. Suitable range

For my range of data I will be varying the length of wire by 10cm, from 100cm-10cm doing this I will try to find a relationship between the current and the length of the wire.

Preliminary experiment

In my preliminary experiment I used the following equipment to carry out an experiment as accurate as I can.

Constantan Wire (100cm)image00.png

Cell two batteries

Switch

Circuit Wires

Crocodile Clips

Scissors

Meter Rule

Ammeter

I obtained these results:

Preliminary experiment results

Length of wire (cm)

Current (amps)

1000/length

100.0

0.29

10.0

90.0

0.31

11.1

80.0

0.35

12.5

70.0

0.39

14.3

60.0

0.44

16.6

50.0

0.49

20.0

40.0

0.57

25.0

30.0

0.73

33.3

20.0

0.91

50.0

10.0

1.07

100.0

On the next two pages are my graphs for the preliminary experiment, taken from my preliminary results.

Preliminary experiment analysis

The basic trend of my graph (1000/length) is that as the length decreases the current increases and it is in proportion. I am hoping that I will get similar results, but I expect them to be more accurate and hopefully I will find it easier to make a conclusion.  

Obtaining

I used the following equipment:

Constantan Wire (100cm)

Cell two batteries

Switch

Circuit Wires

Crocodile Clips

Scissors

Meter Rule

Ammeter

Variable Resistor

...read more.

Conclusion

Where are the anomalies?

In graph 4, there is one anomaly it is off the line of best fit, I have calculated 1000/length for 11cm (length) to see if my cutting of the wire is wrong.

      1000/11= 90.9,                91cm

Therefore this is much more closer to my line of best fit. Therefore I can say that mis-cutting the wire by only one centimetre can have a significant effect later on in my results and graphs.  

Ways in which I may of gone wrong:

image01.png        Inaccurate cutting of wire

image01.png        Inaccurate results

image01.png        May not of kept the room temperature at a constant level

image01.png        The crocodile clips may not been connected to the wire properly

image01.png        Loose connection

image01.png        May not of been constant room temperature

Improvements:

 · I could also have made the experiment contain more values, e.g. go from 1-5V instead of just 0.50v this would mean I would get more results, and the average result would have been more accurate, as the anomalies wouldn’t affect the results as much.

· An improvement I could have made is to have kept the temperature constant, and made sure of this by keeping the length of wire in a water bath at a constant temperature.

Further Investigation:

  • Keeping the length constant but varying the thickness of the wire. Seeing if the resistance or current changes when I use a fat or thin constantan wire.
  • I could use different materials like carbon or lead and see if it matters when I change the material.

...read more.

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