To find out what factors affect the resistance of a wire (besides current of temperature)
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Aim: - To find out what factors affect the resistance of a wire (besides current of temperature.) We must use two different variables. Variables: - Variables Chosen 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.
When doing type of wire because the thickness is in Swg I will need to know it in mm: - Swg mm 22 0.71 24 0.56 26 0.45 28 0.37 30 0.31 32 0.28 34 0.24 36 0.20 Diagram: - Fair Test: - Variables Constants Things to change Length of wire Volts (Apart from the repeats on the rheostat) Length of wire. Type of wire Volts (Apart from the repeats on the rheostat) Type of wire. (Vary the thickness) To ensure that the experiment is fair I will: - Make sure that there are no crossovers in my piece of wire so that it does not short circuit. Make sure that I mark with the wire cutters exactly where I muse clip the clips. (1cm in from each end.) I must record the results accurately. I must do three repeats using the rheostat. I must select the correct amount of volts. I must make the wire the correct length. Results: - Length of wire: - Repeat Length (cm) Voltage (Volts) Current (amps) Resistance (Ohms) 123 100100100 0.300.600.90 0.22 0.34 1.17 1.5361.3761.698 123 909090 0.300.600.90 0.46 0.35 1.33 1.5521.7860.667 123 808080 0.300.600.90 0.54 1.27 1.19 1.1950.2640.411 123 707070 0.300.600.90 1.54 0.43 0.88 0.5561.3951.023 123 606060 0.300.600.90 0.59 1.16 1.60 0.5080.5170.563 123 505050 0.300.600.90 2.12 1.17 2.97 0.2370.5130.303 Type of wire: - Repeat Type of wire Voltage (Volts)
If you had a crack in you house on the wall and you wanted to find out if it was getting wider. Set up apparatus just like circuit shown in the diagram. You will need a voltmeter, ammeter, battery pack (6volt pack), six wires and a piece of Measure out a piece of wire at 102cm and mark in 1cm at each end then clip it right on the 1cm mark. 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. Place the wire over the crack glue the clips to the wall. 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. You could stick the wire across the crack and measure the resistance. The wire would be floppy at the moment. You could then come back after a month and measure the resistance again. If the resistance had increased the wire would have got longer. Therefore the crack would have widened. The apparatus will rest on the floor.
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