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In this investigation we are going to investigate the factors affecting the resistance of nichrome wire in an electric circuit

Extracts from this document...

Introduction

Physics investigation

Introduction

In this investigation we are going to investigate the factors affecting the resistance of nichrome wire in an electric circuit

Background Knowledge

The first requirement for conduction is a supply of charge carriers that can move freely through the material. In most solid conductors, notably metals, these carriers are thought to be loosely held electrons. For example, copper has one electron for every atom. The free electrons in a solid conductor are in a state of rapid motion, moving within the crystal lattice at speeds calculated to be around 1/1000 of the speed of light. This motion is normally haphazard (like that of gas molecules) and as many electrons with a given speed move in one direction with the same as in the opposite direction with the same speed. There is therefore no net flow of charge and so no current.

If a battery is connected across the ends of the conductor, an electric field is created in the conductor, which causes the electrons to accelerate and gain kinetic energy. Collisions occur between the accelerating electrons and atoms (really positive ions) of the conductor that are vibrating about their mean position in the crystal lattice but are not free to undergo translational motion. As a result the electrons lose kinetic energy and slow down whilst the ions gain vibrational energy

Electrons move round and round the nucleus in paths called orbits.

Middle

 Independent Variable Dependent Variable Controlled Variable I am going to change the length of wire during this experiment. I am going to measure the resistance of the wire by using ohm’s law. current that we pass through the wire.material of the wire.cross sectional area of the wire.Same room temperature.Same wire used for every test.

Prediction
I predict that if the width increases then the resistance will also increase in proportion to the width. I think this because the thicker the wire the more atoms and so the more likely the electrons are going to collide with the atoms. So if the width is doubled the resistance should also double. This is because if the width is doubled the number of atoms will also double resulting in twice the number of collisions slowing the electrons down and increasing the resistance. My graph should show that the width is proportional to the resistance.
Because the width of the wire is only half the width of the wire below there should be half the number of collisions between the electrons and the atoms. The wire below is twice the width of the wire above and so there should be twice the number of atoms resulting in twice as many collisions and a predicted doubling of the resistance.

List of the apparatus

• Power pack supply of up to 12V
• A full scale deflection ammeter with a measuring range of 0-1
• A voltmeter with a measuring range of 0-5 V
• Circuit wires
• Nichrome wire 0.35m in length
• A meter ruler
• Crocodile clips
• Switch
• Pencil

Conclusion

ass="c3">1.8

1.67

15

3

1.25

1.2

1.25

1.23

2.44

20

3

1.00

1.0

1.00

1.00

3

25

3

0.69

0.69

0.69

0.69

4.35

30

3

0.57

0.58

0.58

0.58

5.17

35

3

0.49

0.48

0.49

0.49

6.12

40

3

0.43

0.42

0.41

0.42

7.14

45

3

0.38

0.38

0.39

0.38

7.89

50

3

0.34

0.34

0.34

0.34

8.82

Safety Precautions

There are not many safety precautions that need to be taken into consideration, in this experiment. The main two I can think of are stated below :

• Do not carry out the experiment in wet areas, as water is a very good conductor, and thus could be very dangerous.
• Do not touch the wire when the circuit switched on, because the current would heat up the wire and it may be extremely hot.
• Keep the voltage at a lowish level so as no-one will be electrocuted

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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