• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

To investigate how the resistance, R, of a length of wire, l, changes with diameter, D and determine the resistivity of the material the wire used.

Extracts from this document...

Introduction

A level Physics  

Resistance coursework by Priyesh Patel 12O

Resistance of a Wire

Aim

   To investigate how the resistance, R, of a length of wire, l,changes with diameter, D and determine the resistivity ρ of the material the wire used.

Introduction

   In this experiment, I am investigating the resistance, length and diameter to find the resistivity of a wire. Hence, we use the resistance formula to calculate this:

image00.png

R is the resistance of the conductor in Ohms (Ω)
A is the cross sectional area in m2
l is the length of the wire in metres (m)
ρ is the resistivity of the material in Ohm metres (Ωm)

   Three external factors influence the resistance in a conductor. Thickness (cross-sectional area of the wire), length, and temperature all have some effect on the amount of resistance created in a wire. The fourth factor is the resistivity of the material we are using. 

The wires which are available for use are:

Constantan (mm)

Nichrome (mm)

Cross sectional area (x 10-8m2) 2.d.p

0.19

2.80

0.23

4.10

0.28

0.28

6.10

0.31

0.31

7.50

0.37

0.37

10.70

0.40

12.50

0.45

0.45

15.90

0.56

24.60

0.71

39.50

0.90

63.50

1.25

122.20

   I found that it would be better to use the constantan wire because of the range of diameters, hence a wide range of cross sectional areas of wire are available. The temperature coefficients of the resistance for a constantan and nichrome wire are shown in the table below:

Substance

Temperature coefficient of resistance (K-1)

Uses

Constantan

0.000010

Standard resistors

Nichrome

0.00040

Heating elements

The resistance of most materials varies with temperature, in a metal, an increase in the temperature causes a greater vibration of the atoms in the fixed framework of atoms, and hence there is more interaction between these vibrating atoms and the flowing electrons. This results in the resistance of the metal rising as the temperature increases.

...read more.

Middle

If I double the cross sectional area of the wire, then I will cut the resistance by half. This is because a wide wire would allow a high current to pass through it, while it would be more difficult for the current to flow in a narrow wire due to it’s restriction to a high rate of flow.The resistance would be higher for a thin wire compared to that of a thick wire because of the increase in collisions of electrons and the metal ions.
Accuracy

   I will make my experiment as accurate as I can by using accurate measuring apparatus, such as the micrometer, a digital multi-meter instead of the traditional analogue voltmeter, as the scale divisions are much smaller on the digital meter than on the analogue meters.

   I will try to make sure there are no kinks in the wires as this increases the thickness of the wire. I shall measure the diameter from a number of places on the wire so that I can see that the wire is of one diameter on the length.

   I will have to take account of possible errors, such as the zero error in equipment, and other random and systematic errors, which can occur.

   I will try to avoid making the parallax errors, (the error which occurs when the eye is not placed directly opposite a scale when a reading is being taken). This can be made on reading off a ruler. The reading errors (the error due to the guess work involved in taking a reading from a scale when reading lies between the scale divisions, and the zero error (the error which occurs when a measuring instrument does not indicate zero when it should)

...read more.

Conclusion

-8Ωm.

   So if I were to find the uncertainty in the value for the resistivity, I would have to use the following formula: -

% Uncertainty

=

(½(max gradient-mingradient))

X

100

Gradient of line of best fit

% Uncertainty

=

(½(50.00 x 10-8Ωm -46.80 x 10-8Ωm))

X

100

48.60 x 10-8Ωm

% Uncertainty

=

1.60 x 10-8Ωm

X

100

48.60 x 10-8Ωm

=

0.03292181

X

100

=

3.29%

   However, as the gradient on the graph was equal to the resistivity x length, I have to add the error in length to find the possible error in the overall experiment.

Total % Uncertainty

=

% Uncertainty in resistivity + % Uncertainty in length

=

3.29% + 0.50%

=

3.79%

   Now, I have to calculate the error from this percentage uncertainty. You do this by calculating 3.29% of the gradient of the line of best fit.

3.79% of 48.60 x 10-8Ωm

=

0.0379 x 48.60 x 10-8

=

1.84 x 10-8Ωm

 Resistivity

=

(48.60 x 10-8 ± 1.84 x 10-8) Ωm

   This % Uncertainty of 3.79%, tells me that the procedure or method I used is quite accurate, by looking at the size of the possible error of ± 1.84 x 10-8Ωm. However, it also tells me that there is some room for improvement, such as repeating readings for accuracy and taking the average. The largest % Uncertainty was in the current, this being because I had used an analogue ammeter, if I had used a digital ammeter, the % Uncertainty would have reduced to 1.56%.

   Overall, on looking at the actual resistivity, from “Physics For You”, I believe that my results were accurate, but taking the errors into account there is a possible range in my resistivity being between: 46.76 x 10-8 Ωm – 50.44 x 10-8 Ωm. This tells me that the resulting error is a major contribution to the resistivity, as this error can have a huge effect on the resistivity of the constantan wire I used. However, on doing this experiment again, I would know what to look out for, i.e. specific errors, change of equipment, i.e. the steel rule and digital meters.

Bibliography

“Physics For You”

By

Keith Johnson

“Dictionary of Science”

By

C. Stockley

Simmone Hewett

C. Oxlade

Sue Holt

J. Weitheim

John Miller

...read more.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

Found what you're looking for?

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

Here's what a teacher thought of this essay

4 star(s)

This is a well structured report.
1. There is a running commentary through this investigation that should be removed.
2. The report needs to have a 'Variables' section that contains information is that spread throughout the report.
3. The report is incomplete and needs to be finished.
****

Marked by teacher Luke Smithen 05/09/2013

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 GCSE Electricity and Magnetism essays

  1. To investigate which fuel gives out the most energy when burnt. We are burning ...

    315KJ/MOL From the preliminary test I have decided to make the following improvements: * Burette In my preliminary I used measuring cylinders to measure the 100cm3 of water. In my actual I will be using a burette to ensure accuracy and to make sure that the test is fair.

  2. Electromagnets - What factors affect strength of an electromagnet?

    Make sure that the wire is wrapped tightly and close together. 3. Connect the power pack with two wire ends. 4. Connect the variable resistor to the power pack. 5. Connect the ammeter in series. 6. Connect the electromagnet with the ammeter.

  1. An Experiment To Find the Resistivity of a Wire

    PREDICTION I assume that as the length of the wire increases, the Resistance of the wire also increases. I also believe that the rate at which it increases will be directly proportional to the length (i.e. R ? L.) --------------------------------- 1 This is because a property of atoms of all

  2. Investigating how the resistance of Nichrome wire depends on its length

    the needle is focused on one set unit of current for all three repeats and for all the lengths that will be measured. Material of wire will be kept constant as we will be using the same type of wire for all the lengths that we will be using (we

  1. Free essay

    Resistance in a wire

    The shortest measured length of 10cm acquires the least resistance, therefore my prediction suggests as the length increases the more resistance generates and the current will weaken. The longer wire introduces more ions throughout the length or the wire therefore more resistance is present.

  2. An experiment to find the resistivity of nichrome

    I then plotted a graph of the length of the wire against average resistance and used it to calculate the resistivity of nichrome as mentioned in my plan where the average resistance can be calculated using the relation??? R=??V .

  1. The Bouncing Ball Experiment

    I would say that my results are probably quite reliable because we made every effort to make the trial experiment fair, and my results turned out to be as I expected. The purpose of the preliminary experiment was to give me an idea of how my real thing would go so I would be prepared.

  2. How does the Thickness of Wire Affect Resistance?

    This line shows a rapid decrease in R in section A, and a slower decrease in section B. I predict that if I were to extend my experiment the resistance would 'level out' to a lowest resistance, but wouldn't get any lower than that point.

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