• 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

# 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)

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.

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.

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

# Related GCSE Electricity and Magnetism essays

1. ## Factors Affecting The Resistance Of A Metal Wire.

4 star(s)

Current (A) Voltage (V) Resistance (?) 50 0.130 1.220 9.380 100 0.080 1.380 17.250 150 0.060 1.510 25.167 200 0.040 1.580 29.500 250 0.040 1.610 40.250 300 0.030 1.620 54.000 Repeat 2 Length of Wire (cm) Current (A) Voltage (V) Resistance (?) 50 0.200 1.810 9.050 100 0.110 1.950 17.730 150 0.070 2.000 28.580

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

5. Find the resistances (by using the formula R=V/I) and write them down. 6. Record all results in a table, then do graphs and charts plotting the lengths against the Current (amps), Voltage (volts), and the resistance (ohms). Results: Below is a table of results showing the recordings for currents, voltages, and resistances; Length of wire (cm)

1. ## An in Investigation into the Resistance of a Wire.

0.31 0.11 2.82 0.45 0.16 2.81 0.79 0.28 2.82 1.68 0.60 2.80 55 0.20 0.08 2.50 2.47 (2.5) 0.27 0.11 2.45 0.39 0.16 2.44 0.62 0.25 2.48 1.01 0.41 2.46 50 0.18 0.08 2.25 2.30 (2.3) 0.28 0.12 2.33 0.39 0.17 2.29 0.69 0.30 2.30 1.61 0.70 2.30 45 0.17 0.08 2.13 2.12 (2.1)

2. ## Resistance of a Wire Investigation

rough trials, it was decided that 3V would be used in the proper experiment, as it provided results from 10cm up to 100cm and the higher voltage provided no additional ease of measurement. Furthermore, it was also decided to allow the wire to cool between experiments as considerable heat was

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

my range, I predict that once the magnet saturated I feel the line of best fit on my graph would curve and then continue at a horizontal line. In my experiment I have made a magnet, not by stroking it with another magnet, but by passing an electric current through its magnetic field.

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

However if longer wires do no not have a high resistance the plots on the graph would have been everywhere and it would have been a negative correlation. I have taken notice in most the graphs that when results of the voltmeter increases the current in the ammeter decreases.

1. ## Resistance and Wires

Conclusion Secondly the second experiment concluded that the thinner that the nichrome wire is, the larger the resistance. This is also evidence to support my prediction. The prediction made concerning the relationship between resistance and diameter of the wire, was in fact correct also.

2. ## Factors Affecting the Resistance of a wire.

For a given length, a conductor with a larger cross section area has a greater number of electrons carrying the current. Hence each electron experiences fewer collisions and therefore the resistance of the conductor is smaller. * Type of material Different materials have different electron densities (number of electrons per unit volume).

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