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# Investigation to test how the length affects the resistance of a wire

Extracts from this document...

Introduction

## Stephanie Clayton 11 S 2

Investigation to test how the length affects the resistance of a wire

In this piece of coursework I will be investigating the resistance of a wire while current is flowing through it.

To make a current flow through a conductor, there must some potential difference and voltage across it. Different types of wires have different amounts of resistance, for example nichrome wire has more resistance than copper wire

Resistance is what slows down the electrical current in a wire. Resistance is a measure of how hard it is to get a current through a component at a particular potential difference or voltage. Resistance can be calculated by using an equation:

## Resistance = potential difference across conductor

current through conductor

There are some factors that affect resistance these are:

## Length-doubling the length of a wire doubles its resistance

### Cross-sectional area-halving the ‘end on’ area of a wire doubles its resistance. So a thin wire has more resistance than a thick one.

Material-a nichrome wire has more resistance than a copper wire of the same size.

Temperature-for metal conductors, resistance increases with temperature. For semi-conductors, it decreases with temperatures.

There is a heating effect whenever a current flows through a resistance.

Middle

2                          slightly warm                      0.19             0.09

3                                warm                           0.42             0.22

4                                warm                           0.67             0.35

5                        increased warmth                 0.92             0.48

6                              quite hot                        1.14              0.6

7                          increased heat                     1.4              0.73

8                              very hot                         1.66             0.88

#### Preliminary Conclusion

In my preliminary experiment I found that the voltage of the circuit produced heat so we had to find the best voltage to use in the final method of the experiment. It is important to get the right temperature as it affects the resistance, so it is important to try and get the temperature stable.

In our results I found that the higher the voltage the hotter the wire became, this is because the greater the voltage the more electrons are being pushed around the wire causing the heat to increase. This occurred with voltages such as 5,6,7, and 8. You can see these results set out on the table on the previous page. So in conclusion to this I know that in my experiment I will use quite a low voltage, i.e. to produce a stable temperature. Therefore I will use a set voltage of 2 volts on the powerpack.

#### Method

• I will start by setting the apparatus up as shown in the diagram above. This will include a voltmeter, ammeter, crocodile clips, connecting wires, length of wire, and a powerpack.
• Then start by putting the crocodile clips at two particular measured points, and by using both an ammeter and voltmeter use these readings to calculate the resistance of that particular length of wire.
•  Then change the length of wire a number of times and record the results on a table as accurately as possible to collect the most reliable results.
• I will have a powerpack set at 2 volts and take measurements at:

10cm

20cm

30cm

40cm

50cm

60cm

70cm

80cm

90cm

• I will increase the voltage so I am able to investigate the differences in measured resistance. I will take measurement every 10cm to achieve a set of accurate results.
• Then I will compare and contrast the results that I collect with my prediction and see if what I thought would happen did? And if not, why not? I will be able to refer back to my prediction and see if my prediction that the resistance would increase in the wire as the length does. My theory being that more collisions of electrons would occur as they would have more energy to collide with each other. Hopefully I will conclude with a set of results to support my theory

Conclusion

Additional evidence which I could possibly produce to support my conclusion would be to extend the enquiry by looking into the possible effects if I were to use different types of wire. A possible procedure would be to set up a similar experiment to the one I used in this current investigation but test 5 different types of wire which would give a possible variety to the amount of resistance produced and compare them to one another. Now knowing that as the piece of wire gets longer as so does the amount of resistance produced I would be able to support this conclusion with the additional evidence to how the type of wire can affect the outcome of resistance.

I can say with confidence that my investigation into the resistance in a wire was most successful. I have proven fact that resistance doubles in according to length and this is what I have learnt. It has provided my with enough information to be able to establish a foundation to investigate further and developed and interest into this issue.

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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