• 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. Resistance of a Wire Investigation

    is used to provide the pondweed with carbon dioxide. Performing the experiment with different volumes of NaHCO3 could vary the amount of CO2. The plant would be kept at a constant distance from the lamp and a constant volume of water would be added to the sodium hydrogen carbonate.

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

    This would have contributed as a slight error in my results. As this factor probably only made a slight difference, it did not affect my results. The crocodile clips and the connecting leads could have affected the fairness of the experiment.

  1. To plan an experiment to measure the extension in a piece of copper wire, ...

    shall increase, in the preliminary and research I have found that if we stretched a copper wire to determine its Young modulus, you'd notice that, beyond a certain point, the wire stretched more and more and will not return to its original length when the load is removed.

  2. How does the length of a wire affect its resistance

    electrons will have to move about, resulting in no collisions as there will be a lot of free space. * As the length increases of a wire, the resistance increases also. A variable resistor or rheostat is used to vary the current in a circuit.

  1. How does length and width affect resistance

    In a series circuit, the total resistance equals the sum of the resistances of each device in the circuit. The addition of devices to a series circuit increases the resistance and thus decreases the total current. But in a parallel circuit, adding devices provides additional paths for the current and decreases the total resistance.

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

    The only problem that can be illustrated is that because low current/voltages will be used, we will not really go over 1 volt. This means that the first figure before the decimal point is "wasted". 2sf though is enough, 3sf would be too accurate.

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

    The reason for this, and not one of the other factors is due to accuracy. Variable Measurement Length Centimetres (cm) Cross-sectional area Millimetres (mm) Substance - Temperature Degrees Celsius (�C) Substance is a discontinuous variable, therefore we cannot find a correlation between it and resistance.

  2. Does the length of the wire affect the resistance?

    This is because the longer the wire the electrons have longer to travel. This means that the electrons will collide more with the wire atoms, causing higher resistance. However if the wire was shorter then the resistance will be very low as the electrons will not have further to travel.

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