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# Physics AT1-Resistance of a wire

Extracts from this document...

Introduction

## Physics AT1-Resistance of a wire

Introduction

The electric current in a solid is a movement of tiny negative charged electrons.  As these electrons move they collide with the particles of the solid which makes the electrons movement difficult.  Resistance is a measure of how difficult it is for the electrons to move.  A high resistance means that the electrons will make lots of collisions and lose lots of energy. 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 bulb is quite thin as needs to resist the flow of particles for the bulb to glow.  Resistance is measured in ohms. The higher the resistance, the lower the current. If there is high resistance, to get the same current a higher voltage will be needed to provide an extra push for the electricity.  Some metals have less resistance than others. Wires are always made out of copper because copper has a low resistance and therefore it is a good conductor. The length and width of a wire also has an effect.

Ohm’s Law: The current is proportional to the voltage, provided the temperature remains constant.

## Factors

The resistance of a wire depends on certain factors.

Middle

Where the wire is position I will have a pair of crocodile clips to hold it in place.  I plan to use 70cm of each nichrome wire and I plan to coil each wire.  To help keep my results accurate I plan to only use a low current when testing;  this will keep the temperature of the wire down.  For each wire I plan to take one reading from the voltmeter at a constant current of 0.5 A.   I then plan to repeat the reading of each wire three times and take the average  result .  I shall then be able to calculate the resistance of the wire using the equation resistance = volts/amps and represent this data in the form of a graph.

Fair Test

I have already mentioned which factor I am investigating and which factors I will keep constant (see pages 1 and 2).  I will do the following things to make the experiment a fair test:

• Use the same material for each wire
• Use the same length of each wire
• Take readings using a low current (keeps temp. down)
• Use same equipment for each test

Safety Precautions

I will take the following precautions and make sure others are safe as well:

• I will wear safety glasses
• I will make sure there are no bag or obstacles on the floor causing a hazard
• I will be careful with the electricity present
• I will not run around
• I will not touch live wires

Method

Apparatus

• Voltmeter
• Ammeter
• 2 Crocodile clips
• 5 nichrome wires (0.28mm, 0.31mm, 0.40mm, 0.45mm, 0.50mm)
• Power Supply Pack
• Circuit wires

Conclusion

Even though there is a result which doesn’t fit the pattern, the majority of results still follow my prediction.

Improvements and Evaluation

Although I took precautions to ensure this was a fair test, there were some areas where accuracy could have been improved.  The anomalous result suggests that I would need to repeat at least that part of the experiment for that width of wire.  It could be that I didn’t accurately measure out 70 cm of wire or I didn’t read the voltmeter correctly.  However, I think this last explanation is unlikely because I read the voltmeter three times and each time the reading was almost the same (4.2,4.3,4.2).  This suggests to me that the reason for this discrepancy is more likely to be an inaccurate measurement of either the width or length.  There is also the question of whether the current was measured accurately.

Repeating my results more than 3 times would further improve my results and maybe correct the anomaly.  To improve my experiment I should have taken more time making sure wires are correct lengths and thickness.

Further work that could be done is to look at each wire in more detail.  Trying more currents and investigating more factors for example or maybe trying more diameters of wires would be further ideas.

Bibliography

I used the following resources for research:        Physics For You Textbook

Key Science Physics Textbook

Time for Physics Textbook

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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