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Resistance of a wire

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Introduction

GCSE Physics Coursework                M. Salah Uddin

INTRODUCTION

This investigation is about find the resistance of a wire. Resistance is the slow-down of the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long.
e.g. The filament across an electric light bulb. Resistance is measured in a unit called an ohm (Ω). In 1826, Georg Ohm discovered that:
the current flowing through a metal wire is proportional to the potential difference (p.d) across it (providing the temperature remains constant). The formula for calculating resistance is:

Resistance, R=p.d across the wire (V)/current through the wire (I)

R=V/I

There are four factors affecting resistance:

•length

•cross-sectional area

•material

•temperature

Electricity has a lot of different uses. It can:

•heat things up

•magnetise things

•produce light

•break down some solutions and compounds.

Electric charge is measured in coulombs (C). Positive charges are called protons, and negative charges are called electrons.

Electric current is the moving electrons through a conductor of electricity. Electric current is measured in amperes or amps (A).

A statistical analysis of the experiments will be done in this investigation.

AIM

...read more.

Middle

SAFETY PRECAUTIONS

•Lab coats

•Gloves

•Safety goggles

•Use DC (Direct Current)

•Make sure power pack is switched of, when not in use

•Make sure that nothing is wet, to avoid electrical disasters.

RESULTS

The results of experiment 1 will be shown first, which was the one where copper wire was used:

Length of wire (cm)

Voltage(V) (Volts/V)

Current(I) (Amperes/A)

Resistance(R) (Ohms/Ω)

10

0.01

1.99

0.005 (3dp)

20

0.02

2.00

0.010

30

0.03

2.01

0.015 (3dp)

40

0.04

2.03

0.020 (3dp)

50

0.05

2.04

0.025 (3dp)

60

0.06

2.06

0.029 (3dp)

70

0.07

2.09

0.034 (3dp)

80

0.07

2.11

0.034 (3dp)

90

0.08

2.12

0.038 (3dp)

100

0.09

2.15

0.042 (3dp)

The formula, R=V/I was used to work out the resistance for each length.

The scatter graph below is of the resistance found when testing the copper wire. It also shows the line of best fit.

image01.png

...read more.

Conclusion

EVALUATION

The investigation went quite well as the results matched the hypothesis exactly. The theories and the predictions were proven correct as I have already mentioned in the conclusion.

The method was carried out step-by-step, and there weren’t any changes made. The aim of the investigation was achieved, which was: to find out how the length of a wire affects the resistance in an electric current. This was done by presenting the data in tables and drawing graphs in the results section.

The investigation could have been improved by doing a few more tests on the wires and not just doing one test each, on the two wires. Unfortunately, enough time was not given therefore a few more tests could not be carried out.

Safety measures were taken when doing the experiment. An example of one of theses is, my lab colleagues and I made sure that our hands were dry when we carried out the experiment.

Overall, I have enjoyed this investigation and learnt that as the length of wire increases, the resistance increases. I found this investigation quite difficult as it was my first time doing an experiment which needed a complete circuit to be set up as I had not done this before. Even though it was pretty hard for me, I still enjoyed doing the experiment and I’m glad to say that I learnt something new from this investigation.

...read more.

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