• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
Page
  1. 1
    1
  2. 2
    2
  3. 3
    3
  4. 4
    4
  5. 5
    5
  6. 6
    6
  7. 7
    7
  8. 8
    8
  9. 9
    9
  10. 10
    10
  11. 11
    11
  12. 12
    12
  13. 13
    13
  14. 14
    14
  15. 15
    15
  16. 16
    16
  17. 17
    17
  18. 18
    18
  19. 19
    19
  20. 20
    20
  21. 21
    21
  22. 22
    22
  23. 23
    23

Physics - Resistivity

Extracts from this document...

Introduction

image04.pngimage05.png

PHYSICS

AIM

The aim of the experiment I am conducting is to find the resistivity of a 24 watt light bulb. This will be conducted through a series of experiments which will be followed by some calculations using formulas such as:

image06.png

Or

image07.png

ρ is the resistivity (measured in ohm metres, Ω-m)

R is the electrical resistance of the material (measured in ohms,Ω)

image17.pngimage17.png is the length of the piece of material (measured in metres, m)

A is the cross-sectional area of the material (measured in square metres, m²).

There are other equations that could be used to work out electrical resistivity, such as:

image25.png

E is the magnitude of the electric field (measured in volts per metre, V/m);

J is the magnitude of the current density (measured in amperes per square metre, A/m²).

Finally, electrical resistivity is also defined as the inverse of the conductivityσ (sigma), of the material, or:image26.png

Electrical conductivity or is a measure of a material's ability to conduct an electric current. This is because resistivity and conductivity are reciprocals.

I aim to use the first equation to work out resistivity by re-arranging it, like so:

image14.png

So if I can measure ‘R’, being resistance, ‘A’ being cross sectional area and ‘l’ being length of a light bulb, I can use the latter equation to work out the resistivity of the light bulb.

RESISTIVITY

The resistance of a wire depends on quite a few factors; these will affect the wires in many different ways, such as temperature increasing resistance. The length of the wire will make a difference. This is because when you have a long wire, the electrons have to ‘squeeze’

...read more.

Middle


IMPLEMENTING

This is how my final circuit looked; I have included the EMF of the power supply and the power of the lamp in this diagram. image11.png

After conducting my first repeat, I got the following results:

EMF

Voltage across bulb        (V)

Current across bulb        (I)

Resistance of bulb (V/I)

12

10

1.96

5.10

12

9

1.85

4.86

12

8

1.73

4.62

12

7

1.62

4.32

12

6

1.5

4.00

12

5

1.36

3.68

12

4

1.23

3.52

12

3

1.07

2.80

12

2

0.9

2.22

12

1

0.69

1.45

12

0

0


On the second repeat I got the following results:

EMF

Voltage across bulb        (V)

Current across bulb        (I)

Resistance of bulb (V/I)

12

10

1.55

6.45

12

9

1.46

6.16

12

8

1.36

5.88

12

7

1.26

5.56

12

6

1.16

5.17

12

5

1.04

4.81

12

4

0.92

4.35

12

3

0.78

3.85

12

2

0.63

3.17

12

1

0.4

2.5

12

0

0


On the third repeat I got the following results:

EMF

Voltage across bulb        (V)

Current across bulb        (I)

Resistance of bulb (V/I)

12

10

1.55

6.45

12

9

1.45

6.21

12

8

1.38

5.80

12

7

1.28

5.47

12

6

1.18

5.08

12

5

1.06

4.72

12

4

0.94

4.26

12

3

0.82

3.66

12

2

0.66

3.03

12

1

0.51

1.96

12

0

0


On the forth repeat I got the following results:

EMF

Voltage across bulb        (V)

Current across bulb        (I)

Resistance of bulb (V/I)

12

10

1.51

6.62

12

9

1.43

6.29

12

8

1.34

5.97

12

7

1.25

5.60

12

6

1.16

5.17

12

5

1.05

4.76

12

4

0.94

4.26

12

3

0.81

3.70

12

2

0.68

2.94

12

1

0.52

1.92

12

0

0


ANALYSING

So I can see the general trend of my results, and spot any anomalous data, I have drawn a simple I-V graph, which includes all my repeats.

image12.png

As you can see from this graph, my repeats 2 to 4 are very similar but my first repeat isn’t.

...read more.

Conclusion

The actual limitations of my experiment that I couldn’t control were things like, external temperature, obviously the limitations of the equipment I used couldn’t control the environmental temperature around the experiment, so I haven’t taken into account any change in temperature as it is out of my control so I couldn’t do anything about it. Also the accuracy and precision of my voltmeter and ammeter would have an effect on my results, this would cause a systematic error and so my graph’s gradient and thus calculated resistance would still be the same. There could also be random fluctuations in the school’s power supply, or in my power pack, which could result in a temporary random error in my results. I don’t think this happened though, as all my data was very similar, excluding the first repeat. Apart from these factors I think my results are reasonably accurate and precise, they were what I predicted and my 2nd, 3rd and 4th repeats proved to be precise.

I think next time I conduct this experiment; I could do it in a controlled atmosphere, so environmental factors, like temperature and pressure don’t have as much of an effect.

The actual value of resistivity for tungsten is  0.0000000528 Ωm at room temperature. The value I got for this according to my results is: 0.0000054 Ωm. This difference would be because of the level of control and accuracy that I had over my equipment and environment. I think that to do this experiment and get the results nearer the standard value of resistivity for tungsten I would need to have this control over the environment, I would need to do more repeats, I would need to take a lot of other factors into account and I would need to use expensive voltmeters and ammeters, that will provide a better accuracy and precision.

...read more.

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

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. In this experiment, we will measure the e.m.f. and the internal resistance of a ...

    Secondly, the set-up of the experiment is used for long time or the switch is plugged on for a long time, it will produce heat to the set-up and then the resistance of the set-up will increase. As a result, the calculated internal resistance of the dry cell will be

  2. Finding the Resistivity of a Wire

    To prevent the wire from getting too hot, thus being a burn hazard, I will keep the current constant at a relatively low value of 0.50A. I will also turn off the equipment when I am not taking measurements. o I will limit the current to 0.50A and switch off

  1. The potato - a source of EMF

    Or in my words, the Maximum Power output can be achieved from the potato cell to the load can be achieved when the internal resistance is equal to the load resistance. By observing what values of resistance the peaks of the curves are I can then see if it matches

  2. Investigation On The Resistivity Of Apples. Since we are measuring the resistance of an ...

    This means that the data is not accurate, hence I am not extremely confident with my results. Discussion The main trend in the graph is that as length increases, the resistance increases linearly. There is a moderate positive linear relationship between the dependent and independent variable.

  1. Investigating the effect of 'length' on the resistance of a wire

    Those which do not are called insulators. Metals behave as conductors because of their structure. In a metal structure the metal atoms release their outermost electrons to form an 'electron cloud' throughout the whole structure. In other words, the atoms in a metal exist as ions surrounded by an electron cloud.

  2. Investigation into the resistance of a filament lamp.

    Then pass the light from this slit through a prism. Shine the resulting 'rainbow' on a white piece of paper and carefully note the colours that are present (it would be helpful to do this in a very dark room).

  1. Does the length of a conduction putty affect its resistance?

    I will also ensure that there is no water near my workbench, as water carries the current and so I could get electrocuted from any water nearby. 2. I will use Digital multi-meters in all of my experiments, in order to ensure that the readings I obtain for both Potential Difference and Current are as accurate as possible.

  2. The Purpose of my sensing circuit is to regulate the temperature in a Steam ...

    1.89 1.88 46 1.95 1.94 1.95 1.94 1.95 1.95 1.95 1.94 1.94 1.95 44 2.01 2.02 2.02 2.03 2.03 2.02 2.03 2.02 2.01 2.02 42 2.06 2.07 2.06 2.07 2.07 2.06 2.06 2.06 2.06 2.06 40 2.13 2.14 2.13 2.14 2.13 2.14 2.13 2.14 2.13 2.13 38 2.19 2.18 2.18

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work