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Investigating the factors that affect resistance of a wire.

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Introduction

Kate Rothery 10M Physics Investigation Investigating the factors that affect resistance of a wire. The aim of this investigation is to investigate how different factors affect the resistance of a wire. Resistance is the ability of a material to resist the current flowing across it. Ohm's law states that the current flowing through a metal wire is directly proportional to the potential difference across it (providing the temperature remains constant). Resistance is measured in Ohms. Resistivity is the amount of resistance of a substance. An electrical current is the flow of electrons from negative to positive. A cell or battery pushes electrons around the circuit as it provides a slope, also known as the potential difference (volts). There are 4 different variables that we could investigate; * Temperature of the wire * The length of the wire * The material that the wire is made of * The cross sectional area of the wire How the temperature of the wire affects resistance An increase in temperature make lattice (patterns of atoms found only in solids) ...read more.

Middle

Therefore the current is doubled and the resistance is halved. Resistance is directly proportional to 1 Area Therefore Resistance is inversely proportional to the cross sectional area of a wire. Investigating how the length of the Wire affects the resistance of the wire Fair Test It is very important that this investigation is a fair test; therefore all the other variables apart from the length of the wire must be controlled. To control the temperature of the wire the current must be kept very low so that the temperature of the wire does not increase. If it did so then the resistance of the wire would increase. A current of 0.1 Amps was decided on, and this must be the same for every test I make. To keep the diameter and the material of the wire constant I will use the same piece of wire for each test. This means that the material and diameter remain the same. The diameter and material of the wire also affect its resistance so it is important that they are kept constant. ...read more.

Conclusion

This enabled me to see which type of wire gave the best range of readings so that they were easy to plot as a graph. I chose Nichrome wire with a diameter of 0.38mm because it gave the best range of results. It also enabled me to see what voltmeters and ammeters would be most suitable for my experiment. I chose an ammeter with a scale of 0 to 2.5 amps because it was most accurate for the current I have decided to use for all my experiments and shows 0.1A clearly. I chose to use the multimeter to record the potential difference across the wire because it had a scale of mV and is more accurate than the other voltmeters. Predictions I predict that as the length of the wire increases so does the resistance of the wire. This is because as the length of the potential slope increases the gradient of the slope decreases. This means that the current flowing through the wire is less and therefore the resistance of the wire has increased. This is what I predict my final graph will look like. The length of the wire and the resistance of the wire are directly proportional. ...read more.

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