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An Investigation into Finding the Different Values of Resistance with Different Lengths of Wire.

Extracts from this document...

Introduction

Name: Luke Smallwood                                   

Group: 10J3

An Investigation into Finding the Different Values of Resistance with Different Lengths of Wire

PLANNING

Aim

In this experiment I intend to find out what happens to the resistance of a wire, when we increase or decrease the length of the wire.

Variables

Input Variables:

  • Length of tested wire.

Output Variables:

  • Ammeter reading and voltmeter reading.

Controlled Variables:

  • The tested wire,
  • Power supply,
  • The leads connecting the components together,
  • The ammeter and voltmeter.
  • The resistor

Prediction

I predict that in this experiment the results will show us that the longer the wire the more resistance the wire will have, and that if the wire doubles in length, the resistance will double. I also predict that the results graph will look similar to the one below:

image19.png

Scientific Knowledge

I have predicted this outcome for my experiment due to the scientific knowledge that I have obtained. I predicted that the longer the wire the more resistance there would be, because when a voltage is applied across the wire, it causes the electrons to move creating a flow of current.  When an electron collides with atomic nuclei, it looses its energy and this is called resistance.

Therefore the longer the length of wire the more atoms there are for the electrons to collide into so therefore there will be more resistance and so that is why I have

...read more.

Middle

image12.pngimage14.pngimage06.pngimage01.png

Method

  1. Set up the apparatus as shown in the circuit diagram above.
  2. Set the crocodile clips so they cover 20cm of the tested wire and then record the result shown on the ammeter and voltmeter.
  3. Then record the current and voltage for 40cm, 60cm, 80cm and 100cm, but in between each experiment wait for the wire to have a chance of cooling down.
  4. Repeat the experiment two times.
  5. Calculate the resistance for each length of wire for each experiment by using R=V/I.

Preliminary Experiment/Information

I carried out a preliminary experiment because I wanted to investigate which voltage would give suitable readings for my experiment.

I did this investigation by testing three different voltages over 20cm of wire. I tested 9v, 6v and 3v and recorded the current and voltage.

The results were:

Voltage input (v)

Current (amps)

Voltage output (v)

9

0.15

0.1

6

0.1

0.07

3

0.04

0.02

I have not needed to modify my experiment because my original voltage was 6V and my preliminary experiment shows that 6V is a good voltage to be used in this experiment so I will not need to change any variable when carrying out the experiment.  

OBTAINING

Results

Experiment 1:

Cm

1st test

Resistance (ohms)

V=IR

20

V (voltage)

0.07

0.7

I (amps)

0.1

40

V (voltage)

0.13

1.3

I (amps)

0.1

60

V (voltage)

0.19

1.9

I (amps)

0.1

80

V (voltage)

0.24

2.4

I (amps)

0.1

100

V (voltage)

0.3

3

I (amps)

0.1

...read more.

Conclusion

  • Given the wire a longer period of time to cool down,
  • Accurately measured out the lengths of wire,  
  • Used more accurate ammeters and voltmeters, as during some experiments the meters kept on moving from one value to another e.g. 1.8 volts to 1.9 volts.    

The sources of error in this experiment are as follows:

  • The voltmeter readings had to be rounded to the highest figure as the voltmeter on some occasions kept on moving from one value of voltage, to another.

Further experiment

To extend my investigation I could investigate the different values of resistance with different values of voltage.This is how I would go about doing that.

Aim

        My aim for this experiment would be to investigate what levels of voltage would affect the levels of resistance.

Method
  1. Use and set up the apparatus as the same as in the experiment, An Investigation into Finding the Different Values of Resistance with Different Lengths of Wire, but using only a set length of wire to be tested on e.g. 60cm, 80cm, and 100cm.
  2. Using the voltages 3v, 6v, 9v and 12v, measure the current and voltage over the selected length of wire.
  3. Repeat this experiment three times.
  4. Calculate the resistance for each voltage for each experiment by using R=V/I.

Prediction

        I predict that in this experiment, that the higher the voltage, the higher the resistance will be and that the double the voltage, the double the resistance will be, because the more voltage behind the current, offers more chance of the electrons colliding with the atoms in the wire, so therefore offers more chance of resistance.

...read more.

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