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Physics Investigation – Resistance Of Wire. Essay, Research Paper

Aim: -To find out what factors affect the resistance of a wire (besides current of temperature.) We must use two different variables. Variables: -VariablesChosen Variables Length of wire. Thickness Type of wire.Chosen Variable: -I have chosen length of wire as one as my variables because it will give me a good range of results. I will be able to compare the results from the shortest wire to the longest. I will start at 100cm then I will take 10cm off each time until I get to 50cm. (100,90,80,70,60,50cm) The type of wire will also give me a good range of results because I will be able to see if the difference in thickness of wire makes a difference and if the different type of wire makes a difference. (E.g. aluminum and copper.) The thickness will range between 0.71mm and 0.20mm. So I will do as many different types of metal that I can do with in the allotted time.Prediction: -For preliminary work, we tested how the temperature of a circuit can affect the resistance of a bulb filament. We altered the temperature of the wire by changing how much power passed through the wire ? using a rheostat. We found out that the longer the wire the higher the resistance. We used this circuit:Greatly exaggerated in size we have a lattice of tungsten ions. These are positively charged, and vibrating fast, e.g. average speed several hundred m/s. Electrons are free to move about, pushed along by the battery, resisted by tungsten ions that vibrate more and hinder the electrons. Therefore resistance rises as the filament gets hotter but in this experiment as the length increases the resistance increases.As the electrons in an electric current move around a circuit, they bump into the atoms in the wires through which they pass. Atoms of different elements impede the electrons by different amounts. For example, electrons pass easily through copper wire, but much less easily through tungsten wires. We say that copper has a lower resistance than nichrome or tungsten. This is why copper is used for the connecting wires and cables in electrical circuits.When an electric current passes through thin nichrome or tungsten wire, the electrons cannot flow easily. They collide with the atoms in the wire, which vibrate more quickly. This causes the wire to warm up. If the resistance of the wire is high and the current is large, the wire may get red hot. Conductors which provide a high resistance are called resistors.This can be linked to the Ohm?s law. The voltage across a metal conductor is proportional to the current through it, provided the temperature stays constant.Can be written as:V IBecause V is proportional to I, we can say that:V/I = a constantOhm showed that doubling the voltage doubles the current. Treble the voltage will give treble the current, and so on. The larger the resistance, the greater the voltage needed to push each ampere of current through it. This led to the definition of one ohm:A resistor has a resistance of one ohm, if a voltage of one volt will drive a current of one ampere through it.Th resistance of a resistor is the voltage per unit of current, i.e. RESISTANCE = VOLTAGE (volts) (ohms) CURRENT (amps)R = V/ITherefore I predict that the resistance of the wire will increase as the length increases because each electron must travel further throughout the wire and are therefore exposed to more ions and electrons which is equivalent to more resistance. For type of wire I predict that the thicker the wire the smaller the resistance. For type of wire, I predict that the thicker the wire the less resistance and the thinner the wire the greater resistance.I predict that the graph will look like this: -Apparatus: -Ammeter. Rheostat. Battery Pack. (6 volt pack max) Voltmeter. Unknown resistance. 6 wires.Method: -Set up apparatus just like circuit shown in the diagram. You will need a voltmeter, ammeter, rheostat, battery pack (6volt pack), six wires and a unknown resistance. Measure out the pieces of wire to a length of 102cm. I will make sure there is 100cm in-between the clips by making the wire an extra 2cm long and at either end I will measure in exactly 1cm and place the clip their. This will apply when I make the wire shorter. (start at 102cm, then down in tens to 92cm,82cm,72cm,62cm,52cm) When you measure the piece of wire lay it out on a one-meter ruler and hold it and one end and count in the appropriate number. You can re measure it if it is not the correct number. The wire must be straight when being measured. Coil the wire around the pencil and attach to circuit. Make sure no crossovers. (The circuit will short circuit if there are crossovers) Take readings form ammeter and voltmeter. Do three repeats to improve accuracy. Do the repeats by altering the rheostat. One from either end and one from the middle. Record results again. Repeat with different length wire. When doing different type of wire as the variable measure it out to 102cm each time and again measure in 1cm from each end and place the crocodile clips on 1cm in. Then do the same three repeats using the rheostat and then change the type of wire. I will be using the thinner wires so that is why I have gone under 100cm in-between the clips. When attaching the wires make sure that the wire is not long and thin because it will have no amp reading. If the wire is short and fat it will have no volt reading. I feel that doing three repeats will be sufficient because it is a fairly accurate experiment so I think three repeats will be enough.When doing type of wire because the thickness is in Swg I will need to know it in mm: -Swgmm 220.71 240.56 260.45 280.37 300.31 320.28 340.24 360.20 Diagram: -Fair Test: -VariablesConstantsThings to change Length of wireVolts (Apart from the repeats on the rheostat)Length of wire. Type of wireVolts (Apart from the repeats on the rheostat)Type of wire. (Vary the thickness)To ensure that the experiment is fair I will: -Make

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