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# The resistance of copper wire.

Extracts from this document...

Introduction

PHYSICS AS COURSEWORK

NAME: Rameez Ali

TITLE OF EXPERIMENT        The resistance of copper wire

To find out the resistance of copper wire and to work out the resistivity of the copper wire you can use the following equation:  R=ρl

A

PLAN

Middle

1.27V

0.28A

1.29V

0.30A

600mm

1.26V

0.31A

1.24V

0.32A

500mm

1.22V

0.35A

1.20V

0.37A

400mm

1.17V

0.42A

1.14V

0.45A

300mm

1.10V

0.55A

1.09V

0.58A

200mm

0.97V

0.71A

0.98V

0.70A

100mm

0.75V

1.06A

0.73V

1.07A

50mm

0.52V

1.50A

0.51V

1.47A

 Average Voltage Average current Resistance (Avg.V/Avg.C) 1.28V(700mm) 0.29A 4.41Ω 1.25V(600mm) 0.315A 3.97Ω 1.21V(500mm) 0.36A 3.36Ω 1.155V(400mm) 0.435A 2.66Ω 1.095V(300mm) 0.565A 1.94Ω 0.975V(200mm) 0.705A 1.38Ω 0.74V(100mm) 1.065A 0.69Ω 0.515V(50mm) 1.485A 0.35Ω

C2a: raw data recorded

B6b suitable precision

B4c at least 8 readings taken, with repeats

B8d mean values calculated

B2d two units correct

B4d all units correct

B6c clear and accurate presentation

C4b data presented with headings and units

B6a suitable sig. figs

Processed data

C2b equations used C2c p.d. recorded

C4a p.d. correct

A list of possible sources of random error

• Accidental adjustment of the voltage.
• Placing the crocodile clips slightly out of place.
• The crossing over of the wires.
• Faulty power packs, ammeter or voltmeter.

D2a

A list of possible sources of systematic error

• Faulty power packs, ammeter or voltmeter.
• The use of copper wire with a high level of impurities or long-term exposure to air.

Conclusion

D2d

Statement of theory related to investigation

Electrical resistance is the ratio of the potential difference (i.e. voltage) across an electric component (such as a resistor) to the current passing through it:

or

(where V is the voltage and I the current)

It is thus a measure of the component's opposition to the flow of electric charge. Electrical resistance is usually denoted by the symbol R. The SI unit for electrical resistance is ohm. Its reciprocal quantity is electrical conductance measured in siemens.

For a wide variety of materials and conditions, the electrical resistance does not depend on the amount of current flowing or the amount of applied voltage: the two are proportional and the proportionality constant is the electrical resistance. This is the content of Ohm's law.

As the length doubles the resistance doubles. Resistance is caused by electrons bumping into ions. If the length of the wire doubles, the electrons bump into the ions twice as much so the resistance will double.

The resistance of a wire at constant temperature depends primarily on its length, its cross-sectional area and its resistivity.

C8a

Written conclusion (with reasons) for what has been discovered

In an overall conclusion based on my predictions and final results, I have found that as the voltage decreases the current increases, and that resistance restricts the flow of electrical charge. Whenever there is a resistance present in a circuit, it will always restrict the flow of current; therefore making it smaller

C8b

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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