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What factors influence the resistance of a wire?

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Introduction

What factors influence the resistance of a wire? Aim: To devise and carry out an experiment to show how one factor influences the electrical resistance of a wire. Plan Factors The factors which affect the resistance of a wire are: * Length of wire * Diameter of wire * Temperature * Material of the wire * Current in the wire Background information Resistance is a force which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. If the resistance in a circuit is high then a lot of energy is used up getting the current through. This energy is mainly changed into heat. An electric heater uses this to produce heat. Another use of resistors is to protect delicate electronic components. If you want to keep the current small to avoid damage, you put a resistor in the circuit with the component. The resistor makes it harder for current to flow and so less will flow. The unit of resistance is the ohm symbol ? large resistances are measured in thousands or millions of ohms. ...read more.

Middle

30cm - 40cm - 50cm - 60cm - 70cm - 80cm - 90cm - 100cm * Using the formula R=V I I will work out the resistance. * I will then repeat the experiment two more times, to make sure my results are reliable. Diagram Equipment Connecting wires Power pack on 2V 1 meter of 0.475mm nichrome wire Crocodile clips Ammeter Voltmeter Safety This is not a very dangerous experiment but despite this I will always handle electricity with care, keep the current low and handle with dry hands. Fair Test To keep this experiment as fair as possible I need to make sure that the length of the wire is measured precisely from the inside edge of the crocodile clips, making sure that the wire is straight when I do this. As if I do not do this all of the time then each time I repeat the experiment I will not be using the same length of wire, therefore making it unfair. I must also make sure that the wire is straight when we conduct the experiment. If it is not, then it may short circuit, also bends and kinks in the wire may affect the resistance. The reading that I take of the voltage should be done fairly promptly after the circuit is connected. ...read more.

Conclusion

is difficult to get an accurate reading of length by eye, as the wire might not be completely straight, it may be of different thickness throughout the length. The method used was good, it got the expected results and the anomalies that occurred were not due to a fault in the method,, but the evidence achieved from this were enough to support a firm conclusion. If I was to do the experiment again, I would use a more accurate method of measurement and also use a rheostat to create even more accurate results. By taking a much wider range of readings and more readings so that a more accurate average can be taken the reliability of the results would improve. I would also let the wire cool down sufficiently in between readings. When the wire heats up, it has lots of energy, which causes the atoms in it to vibrate, making it harder for the electrons to travel. This increases the resistance via another method, so it is not a truly fair test. I would also investigate other factors, such as temperature, thickness, current, and material to see how these would affect resistance in a wire. I would also do the experiment under different conditions such as temperature and pressure to see if they make any difference to the resistance. ...read more.

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