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

Investigating a factor affecting the electrical resistance of a wire.

Extracts from this document...

Introduction

James Crowe

SC1 Investigation 2003

A factor affecting the electrical resistance of a wire

Free Electron Model:

        The free electron model is the representation of a metallic solid as a container filled with a gas composed of free electrons (i.e. those responsible for high electrical and thermal conductivity) and fixed metal ion particles:

The fixed particles, arranged as a crystal lattice, merely vibrate on the spot. The more kinetic energy they have (which can be affected by a rise in temperature) the more violently they vibrate. The free electrons are able to move around randomly within the metal. When a voltage is induced in the wire a current flows, this is because the electrons are attracted to the positive end and repelled by the negative end, as a result of this they move circularly around the circuit.

The origin of electrical resistance is that when the free electrons flow around the circuit, they often collide with the fixed vibrating metal ions which obstruct the flow, this is resistance. As this happens, the collisions cause friction which results in a temperature rise giving the particles more kinetic energy. This means more violent vibrations and so more collisions. Therefore, if a current flows for too long the wire will heat up and the resistance increase. Ohm’s law is a way of using the known voltage and current in a circuit to find out the resistance. Ohm’s Law means a steady increase in voltage would, in a circuit with constant resistance, produces a constant linear rise in current. It is a formulation of the relationship of voltage, current and resistance expressed as V = I x R.

Variables:

        There are many variables which could affect the electrical resistance of a wire. These are the diameter of the wire (its thickness)

...read more.

Middle

Wire 4:  0.315

Wire 5:  0.376

Here are the results of my preliminary work:

Wire Number

Diameter of Wire (mm)

Length of Wire (cm)

Voltage (Volts)

Current (Amps)

Resistance (Ohms)

1

0.193

10

1.25

0.71

1.76

1

0.193

100

1.4

0.08

17.50

2

0.234

10

1.16

0.91

1.27

2

0.234

100

1.38

0.12

11.50

3

0.274

10

1.07

n/a

n/a

3

0.274

100

1.36

0.17

8.00

4

0.315

10

0.98

n/a

n/a

4

0.315

100

1.35

0.23

5.87

5

0.376

10

0.88

n/a

n/a

5

0.376

100

1.34

0.31

4.32

This work clearly shows that wire 1, with the thinnest diameter and therefore the highest resistance, has the widest range of results. Therefore I am going to use wire 1 for my investigation as it will give me the best results. Interestingly, wires 3-5 did not even give results for 10cm within the range of the ammeter as their resistance was to low, and therefore the current to high to give a readable current. It is possible that infact the thicker wires would have given a wider range of results, which is a problem, but the ammeter provided couldn’t read their results so this is unimportant.

...read more.

Conclusion

For further work I would like to investigate the variable of the diameter of the constantan alloy wire. I would investigate whether the diameter of the constantan wire and the resistance of the wire were directly proportional. I would do this by using the same method as my original investigation, but doing so on each of the five wires. This would have given a much more detailed investigation and would also have shown whether the fact that length and resistance are directly proportional is true for every diameter of wire, and if so to what extent. It would also show clearly the relationship between diameter of the wire and resistance. Problems with this would be that doing so many experiments would mean a much higher likelihood of anomalies. It would also be very time consuming to get so many results, so a way of needing to take fewer results for the same conclusion would also be helpful. Problems with equipment and wires heating up and changing resistance would also be more prominent in this further investigation, so these problems would be analyzed more in my further work. I predict that this further work would show that infact the diameter of the constantan alloy wire and the resistance of the wire is indirectly proportional. Therefore if I increased the diameter of the wire the resistance would decrease. This can be shown from the use of the free electron model:

This shows that for the same distance of wire if the diameter doubles then the number of free electrons doubles with the same probability of collisions occurring. Therefore there are twice as many free electrons to flow around the circuit resulting in half the resistance. This means that as they are indirectly proportional then doubling the diameter of the wire would half the resistance. This is what my further work would show, in investigating the variable of the diameter of the constantan alloy wire.

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

    Do this again for all the lengths (going down in 10cm) until you reach 10cm. 4. Get 3 readings for each length to make sure you get accurate readings, then find the mean averages for each length. 5. Find the resistances (by using the formula R=V/I)

  2. An in Investigation into the Resistance of a Wire.

    13 4.12 (4.1) 0.41 0.10 4.10 0.62 0.15 4.13 1.07 0.26 4.12 2.02 0.49 4.12 85 0.31 0.08 3.88 3.90 (3.9) 0.35 0.09 3.89 0.47 0.12 3.92 0.63 0.16 3.94 1.21 0.31 3.90 80 0.30 0.08 3.75 3.73 (3.7) 0.37 0.10 3.70 0.52 0.14 3.71 0.89 0.24 3.71 1.19 0.32 3.72 75 0.49 0.14 3.50 3.51 (3.5)

  1. Resistance of a Wire Investigation

    Voltage (V) Current (A) Resistance (W) (to 2 d.p.) 10 Could not be carried out as the wire simply melted. 20 2.12 2.07 1.02 30 2.25 1.56 1.44 40 2.34 1.24 1.88 50 2.41 1.02 2.36 60 2.45 0.88 2.78 70 2.49 0.77 3.23 80 2.52 0.68 3.71 90 2.54 0.62 4.10 100 2.56 0.55 4.65 After performing these

  2. Electromagnetism - investigating what effect increasing the number of turns in a coil on ...

    The wire's magnetic field shape is very spaced out, weak and in large circles, it would take a very long time for this to magnetize a core. For my experiment I changed the shape of the single turn to a long, thin, and compact coil, which is known as a solenoid.

  1. Free essay

    How the length of constantan wire affects the ressistance in a electrical circuit

    not clogged up * Most importantly do not increase the voltage of the power pack excessively as the wire will and your safety is in harm How did I ensure a fair test?

  2. Resistance and Wires

    After conducting further manipulation and analysis of the results from the second investigation, it became clear how resistance is affected by area of wire. Results indicate that the smaller the area of wire, the smaller the resistance, however this cannot be trusted because the larger the diameter as shown in

  1. Factors Affecting the Resistance of a wire.

    If the conductor is twice as large there will be twice as many collisions and hence the resistance of the conductor will be doubled (for constant cross sectional area). * Cross-section area (A) A conductor with a larger surface area has a greater number of conduction electrons, as it has a larger volume.

  2. Resistance in a Wire Investigation

    have been slightly inaccurate as the rulers used might not have been exact, and it was difficult to get an accurate reading of length by eye, as the wire was not completely straight, so it may have been of different thicknesses throughout the length.

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