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# How Does the Length of a Wire Affect Its Resistance?

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Introduction

How Does The Length of a Wire Affect Its Resistance?

In this investigation, I will try to find out how the length of

a wire affects its resistance, by carrying out an experiment and

analysing the results to come up with a conclusion. The wire that I

will use in the experiment is called Constantan.

Method

I will set up the equipment as in the following diagram:

The wire is sellotaped to a metre ruler at both ends, a

crocodile clip will connect the wire to the power pack at 0cm.

Another crocodile clip will go from the required length to the

ammeter, and a wire will go from this to the power pack. A voltmeter

will be attached between the two ends of the length of wire, to

measure the voltage between the two clips on the wire.

I have carried out some preliminary trials, in which I varied

the length, and I kept the voltmeter at a constant 1V. I found that

this constant was too low to see a reasonable difference in the

results as the current had decreased so much as the length

investigated grew to 100cm. All of the values for current were found

to be under 0A.

Middle

using the following equation…

RESISTANCE=VOLTAGE/CURRENT

1.5V Constant VOLTAGE IS CONSTANTLY 1.5V

Length(cm)    Amps (A)

Resistance (Ohms)*

Average

resistance(Ohms)

3             0.72/0.76

2.08/1.97

2.025

5             0.43/0.48

3.49/3.13

3.31

15            0.15/0.17

10/8.82

9.41

28            0.08/0.09

18.75/16.67

17.71

10            0.23/0.25

6.52/6

6.26

20            0.13/0.12

11.54/12.5

12.02

30            0.08/0.07

18.75/21.43

20.09

40            0.06/0.06

25

25

50            0.05/0.05

30

30

60            0.04/0.04

37.5

37.5

70            0.03/0.03

50

50

80            0.03/0.03      50                           50

*RESISTANCE- I have calculated the resistance for both Amp or Voltage

values collected. The average resistance is the average of these two

resistances calculated.

Conclusion

III.        We changed the equipment in the 1.5V experiment after we had

taken the measurement at 50cm, as it was the end of the lesson.

The wire was a bit slack, so it may have been a few millimeters

longer than I had measured in the experiment.

I think my results are reliable. They seem to prove the logical

points in my prediction, and show the results that were expected.

There is one rogue point on the 1.5V graph, at (70cm,50 Ohms).

The only explanation for this could be a loose connection when the

experiment was carried out, maybe somebody knocked the circuit. The

results are quite accurate, enough to rely on. The resistances in the

results table were rounded off, so as to make it easier to plot

results and to read from the graphs.

Another way to investigate how the length of a wire affects its

resistance would be to set up equipment as below:

This method measures the voltage across the wire and the

overall circuit’s current in the same way as before…but a rheostat is

used to synchronize the adjustment of the values on the voltmeter and

on the ammeter. This helps to make the result more reliable, by

Kirsty Hole         1

How does the length of a wire affect its resistance?

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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