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Resistance in Wires Investigation.

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Introduction

Resistance in Wires Investigation

Aim

The aim of this investigation is to consider which factors may affect the resistance of wire and then to carry out an experiment to test one or more of these factors.

Research

Resistance is measured by placing an ammeter and voltmeter in a circuit, as below, taking both readings and then dividing the volts by the current. V = I * R

Factors

There are four main factors that can affect the resistance of a wire.

  • WIRE LENGTH – The longer a piece of wire the greater the resistance, this is because the electrons will have further to travel and so there will be more collisions of electrons. Wire length should be directly proportional to resistance.
  • TEMPERATURE – As wire gets hotter the electrons within gain more energy and vibrate causing more collisions between electrons, this increase in collisions means a greater resistance for the hotter wire.
  • TYPE OF WIRE – Different types of wire affect resistance because of atom structure. Wires with more electrons in the outer shell of their atoms will have a greater resistance as there will be more collisions. Also if a wire is denser then there will be greater resistance as collisions between electrons will occur more often.
  • WIDTH OF WIRE – As the width of the wire increases the resistance will decrease because there will be more room for the electrons to move around freely. The increase in space means that there is more space for the electrons to flow freely because there would be fewer collisions with atoms.

Choice of Factor

I have chosen to investigate length as this is the easiest of the four and I believe that we will get the best set of results by doing length. I will be using the wire constantan 22 as this is a very good wire at maintaining a constant temperature, I choose grade 22 as this was the thickest and it heated up the least on my preliminary investigation meaning that it will not be affected as much by temperature in the experiment and so keeping my readings as accurate as possible. Temperature in a wire would be very hard to measure as it would be difficult to alter the temperatures. We could do type of wire but then other factors like temperature come into it as some could heat up more than others, hence altering the resistance.

        I predict that the longer the wire the greater the resistance will be I make this prediction with the scientific knowledge that as it is longer the electrons will have further to travel. Also for this to be correct then we should also be seeing that the resistance is directly proportional. Double the amount of wire should have double the amount of electrons and double the amount of collisions, so therefore a piece of wire 20cm long should have double the resistance of a piece of wire that is 10cm long.

Equipment

  • Power pack connected to the mains
  • Meter ruler
  • Constantan wire
  • Ammeter
  • Voltmeter
  • Crocodile clips and connecting wires
  • Tape
...read more.

Middle

Average

Length

Voltage (Volts)

Resistance(ohms)

Length

Voltage

(Volts)

Resistance(ohms)

100cm

0.88

1.26

100cm

0.89

1.28

80cm

0.7

1

80cm

0.71

1.01

60cm

0.53

0.76

60cm

0.54

0.77

40cm

0.36

0.51

40cm

0.37

0.53

20cm

0.2

0.29

20cm

0.21

0.30

0cm

0

0

0cm

0

0

TEST 2

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Conclusion

        In order for me to improve my investigation I would expand the number of readings I took. Instead of taking just 6, I would take eleven readings, 0cm, 10cm, 20 cm etc. This would give a much better range of results. To give more accurate results I would have it so that we used more accurate equipment, like the voltmeter and ammeter, also it would be better if we could measure the wire more accurately, in order to give us more accurate results. In order to extend the experiment readings could be taken with different currents rather than just 0.7amps.

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