• 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

Investigating factors affecting the resistance of a metal wire.

Extracts from this document...

Introduction

Rhodri Williams        11X        Science Group C

 Investigating into factors affecting the resistance of a metal wire

Plan

Introduction

  Metals can be described as regular rows and columns of positive ions surrounded by a sea of electrons. Each atom in a piece of metal loses one, two or three electrons, which can then move around in the metal:

image02.jpg

                                Positive ionimage00.png

                                Electronimage01.png

Metals conduct because these electrons can be pushed along by a power supply. Resistance comes about because the electrons in a wire continually collide with the stationary ions. So if there is a high resistance, electrons collide with the ions more, so less pass each point each second, so the current goes down.

  A longer wire has more atoms, so more ions, while offering no increase in cross sectional area. Because of this, there are more ions with which the electrons can collide, so there is a higher resistance.

  Different materials will have different resistances, as metals have different distances between atoms, different sized atoms, and different numbers of electrons released. A large distance between atoms means that electrons can get past more easily, so a lower resistance. In a metal with large atoms, there would be a greater chance of an electron hitting one, so a higher resistance than a metal with small atoms. The more electrons released, the more that can pass each point every second, so the lower the resistance.

  An increase in temperature would cause the atoms to vibrate more, so the electrons would have a higher chance of colliding with an ion, so the resistance would increase.

 Increasing the cross section area would decrease resistance.

...read more.

Middle

  •   Finding a method of straightening out the wire. There are two proposed methods:
  1. Hanging the piece of wire from a stand, and attaching weights to it.image08.jpg

  This method works well, but it must be insured that excess weight is not used, as this stretches the wire. Stretching the wire reduces its diameter, so also reduces its cross sectional area, so the measurements taken for a stretched wire are invalid. It is not necessary to use this method for the thinner wires, as they can easily be stretched out by hand using the following method.

  1. Straightening out the wire across a meter rule:

  It is difficult to straighten out the thicker wires with this method, because a large force is needed to do so, and it is easier to provide such a force with the previous method. However, for the thinner wires, this method works perfectly, as they can be straightened out very easily.image09.jpg

Proposed method:

  1.   Straighten out a 1 metre length of nichrome wire by attaching it to a stand clamped to a table and attaching weights weights to the bottom of the wire, or by pulling it across a metre rule. If the method with the weights is used, care should be taken not to let the weights fall on a person's foot, as this could seriously injure them, and the weights should be not so heavy as to stretch the wire.
  2.   Put crocodile clips one metre apart on the wire, and to attach them to a circuit with a power supply with a low voltage and very sensitive ammeter (or a milliammeter if the current is small enough)
...read more.

Conclusion

  There are enough accurate results to be quite sure of my conclusions. Out of the 20 average values taken, only three are not close to the manufacturer's values. That is an 85% success, but it would have been helpful to take readings with more, different diameter wires, but due to time and material constrictions, this was not possible. However, the method I used was not the best possible. If the wire was straightened out along a ruler, human error could result in the crocodile clips being attached slightly wrong, and they are not very thin at the tip, so exactly a meter is very hard to measure out. Therefore, obtaining much thinner crocodile clips would help to make results more accurate. Also, using weights to straighten out the thicker wires would stretch them slightly, giving them slightly lower cross sectional surface areas. To avoid this, it would be necessary to purchase the thicker wires not in coils, but in straight lengths, to give more accurate readings. The measuring instruments used were not the most accurate in existence. However, the most accurate equipment is very expensive, and thus could not be afforded for this investigation.

  There are many other variables that could affect the resistance of a wire. Temperature is one, and this could be tested by insulating the wire being tested, and submerging it in water baths of various temperatures while taking readings. Testing wires of different materials would show whether wires of the same length and diameter but of different metals have the same resistance or not. Varying the length of a wire being tested would show whether the length of a wire affects its resistance.

...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

    The factors affecting the resistance of a metalic conductor.

    4 star(s)

    From the graph, we can see that when we use a wire of length 50cm, and pass current through it, via a series circuit the resistance is slightly less, than when we pass current through two wires of lengths 20cm and 30 cm and connect them with a series connection then the resistance is slightly higher.

  2. Factors Affecting the Efficiency of a Wind Turbine

    The consequence of this is that the air pressure is less above the blade than below. This difference in pressure creates an upward force, which is of course what makes an aerodynamic blade more efficient. Limitations A drag force is always a problem and a major aim in the design

  1. To investigate the factors affecting current in a wire.

    So if the voltmeter reading was above 2V, the rheostat was adjusted so that the voltage was brought back down to 2V. If the voltmeter reading was below 2V, the rheostat was adjusted so that the voltage was brought back up to 2V.

  2. Physics GCSE Coursework:Factors affecting the resistance of a wire

    I was explained and analysed in the introduction and background knowledge, I notice that I can write the equation in the form of the straight line "y=mx", where y = resistance, and x = length. I will use this to link my result's values to the equation and find the constant resistance (p).

  1. Investigate one or more factors affecting the resistance of metal wires

    and I = electrical current (measured in Amps (A)). Limitations of Ohm's Law If Ohm's Law is to be obeyed, the temperature of the wire must remain constant, as mentioned above. It is also necessary that all the physical conditions remain constant.

  2. Discover the factors affecting resistance in a conductor.

    9552.072 6 1.290 0.001290 8.48 6573.43 3 2.350 0.002350 8.43 3587.234 0 0.000 00.00000 0.00 0.000 This table above shows that when the length decreases, the resistance decreases. I hope to see this trend in my main set of results.

  1. Factors affecting Resistance of a wire

    I predict that the resistance will increase steadily as the length becomes greater (i.e. 30cm's resistance will be more than in 20cm, increasing in 10cm increments up to 100cm, which I predict will have the highest resistance of all. In a longer circuit, it is more of a struggle for electrons to get around the circuit without any collisions.

  2. An investigation of the factors affecting the output of a transformer.

    A higher voltage in the primary will cause stronger fields in the core, which causes a higher voltage in the secondary coil. And doubling the primary voltage should double the effect, therefore doubling the secondary voltage. I also think that there will be some loss in efficiency meaning that the transformer is about 80% efficient.

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