• 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

This experiment will show, by using the volts and current to calculate in an equation, how the length of a piece of wire will affect its resistance. The varying length of the wire should back up my scientific ideas.

Extracts from this document...

Introduction

AMALIE SILVANI - JONESPhysics coursework

AN INVESTIGATION INTO HOW THE LENGTH OF A WIRE EFFECTS ITS RESISTENCE

Planning

INTRODUCTION

This experiment will show, by using the volts and current to calculate in an equation, how the length of a piece of wire will affect its resistance. The varying length of the wire should back up my scientific ideas.

Equipment I am using

  • A Voltmetre
  • An ammeter
  • A ruler
  • Wire cutters
  • tape
  • A power pack
  • 5 pieces of wire
  • 2 crocodile clips
  • 1 piece of chosen wire to vary in length

SCIENTIFIC IDEAS

Resistance is caused by electrons colliding with the atoms that metals are closely packed with; this collision slows down the electrons flow. This therefore reduces the current flowing through a circuit. The intensity of the resistance is measured in Ohms (named after its creator George Ohm)

George created a law called “Ohms law”- which states that the current flowing through a metal wire is proportional to the potential difference across it (if the temperature stays the same).

Factors that affect resistance in a wire are:

  • As the temperature increases, the resistance increases.
  • As the length of the wire increases, the resistance increases.
  • As the thickness of the wire increases, the resistance decreases.

The length of a wire also plays a great part in the resistance of the wire.

...read more.

Middle

        I will be using the constantan at a thickness of 28swag throughout the experiment. I found that when I used constantan at 32swag, it burned a lot easier then the constantan at 28swag.

I will be testing the wire at five different lengths- 10cm, 20cm, 30cm, 40cm, and 50cm. I found that this will give me a good, wide spread of results, and give me a clear idea of the pattern.

PREDICTION

I predict that as the length of the wire increases, the resistance will increase. I predict that the voltage readings on the voltmeter will increase as the length of wire increases, and the current reading on the ammeter will decrease. I predict this because as the length increases so will the resistance, therefore the voltage will increase and the current will decrease because it will become increasingly harder for the electrons to flow through the lengthening wire.

FAIR TEST

To ensure a fair test, the experiment will need to be repeated 3 times for each length. If any obvious anomalous results occur during the experiment, I will repeat the experiment until the results are reliable. The following experimental conditions need to be kept constant:-

  • The wire will need to be kept at the same temperature throughout the experiment; this can be achieved by not passing too much current through the wire (keeping the time that the power pack is switched on to an absolute minimum) and waiting in between taking the results for the wire to cool down.
  • Also as this experiment will be carried out in air the room temperature should remain constant.
  • The voltage also needs to be kept constant. I have chosen to use a voltage of 3v on the power pack– after looking at the results of my preliminary experiment (the current is not too high and not to low).
  • The voltage through the circuit will be measured using a voltmeter placed in parallel in the circuit and the current will be measured using an ammeter, placed in series in the circuit- so that I can work out the resistance.
  • To make sure the cross sectional area (thickness) of the wire remains constant, the same piece of wire – with the same amount of swag - will be used throughout the experiment.
  • Ensure the wire remains straight, (but not under tension), so that accurate readings can be taken. I will do this by cello taping it to a 50cm ruler.

To insure that the temperature of the wire doesn’t effect the results as the wire gets hotter due to high currents, I will make sure that the power pack is only switched on for a matter of seconds, and after every recording Is taken I will wait for the wire to cool down (with the power switched off) for approximately 1minute to ensure that the wire is back to its original temperature for a fair test of the next reading.

SAFETY

  • The Voltage input from the power pack will remain at 3volts throughout the experiment and will not be altered with – therefore avoiding the cause of unnecessary wire burning and skin damage.
  • I will not overload the ammeter and voltmeters with current, as this will blow their fuses and they will cease to function.
  • I won’t short-circuit any of the components, or power source.
  • I will act responsibly at all times in the Laboratory with regard to personal safety and the safety of others.
...read more.

Conclusion

There are problems of measuring the actual length as crocodile clips were used. Each crocodile clip is about 5mm broad and has jaws with two sides, which clip on to the wire. It is assumed that the side of the jaw, which was placed at the actual distance that the recording was made, was in fact making the actual electrical contact. However there was no way of determining this at the time of each test. A more accurate result would have beeN possible if a plate had been bolted to the wire at zero and a clamp with a single jaw had been slid along the wire at each measurement. This may have been one of the reasons that the readings taken varied slightly and may be the reason for the inaccurate result obtained at 1050mm.  The actual length measurement could also have been improved if a veneer scale had been used rather a direct visual reading      

When looking at Graph B, (as all of the points lie extremely closely to the straight line), I conclude that the experiment produced very accurate results, even though the apparatus used had its limitations of accuracy.

AMALIE SILVANI - JONES

...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

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. Marked by a teacher

    Draw stress and strain graphs for the metal copper and the alloy constantan. Calculate ...

    4 star(s)

    Figure four shows how alloys and pure metals differ. As can be seen alloy metals have a higher yield stress than pure metals, this is due to their structure makes slipping more difficult. Figure 4 Apparatus: * Table: To conduct experiment on * Wooden Blocks: Helps to keep wire steady and in place when fixed onto the G-clamp *

  2. Investigate how length affects the resistance in a piece of constantan wire.

    Cross-sectional area is impractical, as the size of the measurement is so small, the units are too large to measure accurately with. Temperature is extremely hard to keep constant at a specific point. The rheostat required to keep the temperature constant between 30�C and 100�C would have to be enormous.

  1. Investigating how thickness and length affect the resistance of a wire.

    In addition, if the length of the wire was trebled or quadrupled, then the resistance would also treble or quadruple. From the graph it is easy to tell that the theory is correct and therefore my results reliable. From my results table and graph, I can see that my results that I collected are quite reliable and accurate.

  2. Resistance of a Wire Investigation

    necessary to add sodium hydrogen carbonate to the water to increase the carbon dioxide concentrations. The last inaccuracy, though a small one, was in the time keeping. The main problem here was in when to begin the minute. If for one reading, the minute was started just after one bubble

  1. Factors which affect the resistance of a wire

    The area is proportional to the diameter squared. So if you double the diameter the area increases by a factor of four and the resistance decreases by a factor of four as the two relationships are inversely proportional to each other.

  2. Investigating how the length of a Wire affects its resistance.

    Only one factor should be changed. Current should be kept static as there is a maximum amount of current a wire can have passing through it; it also causes heating which can disrupt results. Voltage, however, is not limited by the wire nearly as much. Because of this, only voltage will change and the current should

  1. To investigate how the length (mm) and the cross-sectional (mm2) area of a wire ...

    The temperature of the wire must also remain constant since the formula does not include temperature as a variable. Since each wire will have a different resistance, I know that I will need a different constant of resistivity in the formula for the wire.

  2. To see how the length of a wire affects its resistance. To find the ...

    * To measure the independent variable accurately we're going use specific apparatus: a metre rule with the different wires attached either end (to measure the voltage and current we're using a standard ammeter and voltmeter).We will also be carrying out the test for each wire 3 times, which will make our results more reliable and accurate when making an average.

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