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# Investigate how the length of a wire affects the resistance flowing through it.

Extracts from this document...

Introduction

Physics coursework
aim: My aim is to investigate how the length of a wire affects the resistance flowing through it.

Scientific knowledge

Current-current is measured in amps. Current is charged particles, which flow from a voltage source through conductive material to ground.

Voltage-Voltage is measured in volts. Voltage is an electric potential difference between two points on a conducting wire. Voltage is like electrical pressure

Resistance-resistance is measured in ohms. It is anything in the circuit that slows the flow down.

Charge is measured in coulombs which is six million million million electrons.

Electrons pass through the wire they collide with fixed atoms this

slows them down.

Collisions occur in the current flowing through a wire; the atoms, which the current the current collides with, are fixed until the current hits them this slows the electrons down. A section of wire will have the same amount of resistance as another piece of wire, which is the same material.

Ohms law states that voltage and current are directly proportional as long as 5the temperature remains constant. This means that if you double the voltage the double the current.

V = IR

Ohms law voltage = current x resistance

Middle

6

0.35

1.33

4.00

8

0.27

1.35

5.00

10

0.21

1.37

7.00

12

0.19

1.40

7.50

My results follow what ohm said and current and resistance are directly proportional.

From these results, I have decided to leave gaps of ten CM in the wire when I do my main experiment this is to get results that are more accurate so I can draw a more accurate conclusion. In my main experiment I will sand down the paper for longer and more methodically to stop the possibility of the rubber insulating the electricity, I will also keep the temperature constant because if the wire get to hot the particles will vibrate more and cause more collisions and therefore more this would reduce current and increase resistance.I had problems with the length of wire moving during my experiment due to it not being very secure. In my real experiment, I will ensure the wire is succoured tightly to the one-meter ruler.

Equipment list

• Voltmeter
• Ammeter
• Power pack
• Copper wire
• Connecting wire
• 1 meter rule
• Crocodile clips
• Sand paper

Step by step guide

• Sand down wire to remove the build up of any copper oxide of coating or to remove membrane that is there to prevent build up of copper oxide.
• Set up equipment as shown in diagram.
• Place crocodile clips on wire 100 cm apart from each other.
• Turn on power pack
• Change the voltage to 0.2v
• Repeat all of the above reducing the distance between wire the crocodile clips each time by 10 cm
• Do this three times to get accurate results and find anomalies

Conclusion

My graphs show me that as the length increases the current decreases this is because the further the current has to go the more particles it will bump into, Thus slowing the current and causing more resistance.

I have also proven my prediction correct and I can not only say that as I increase the length of the copper wire the resistance increases I can say that they are directly proportional. The conclusion of my results shows that the prediction I made at the begging of my experiment based on Ohms law and my preliminary work was correct.
It also proves that Ohms law is correct. Ohms law states, that voltage and current are directly proportional as long as the temperature remains constant. This means that if you double the voltage you double the current. Ohm came up with a number that linked voltage and current for a certain material he called this resistance. Not all my results are exactly doubled or halved as my temperature was not exactly the same for each test only roughly.
If the temperature had not been kept constant then the higher the temperature the more energy the particles have and therefore there is more collisions subsequently giving a higher resistance and making the experiment an unfair test.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

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