To investigate the resistance of a wire Essay Example for Free

To investigate the resistance of a wire Essay In this experiment the factor to be investigated is the resistance of a wire in a circuit when the wires length is altered. This means that all other factors must stay the same or else this would not be a fair test. I am going to investigate how different lengths of wire affect the resistance in a circuit. I am using a voltmeter and an ammeter to measure the current in the circuit after the length of wire is changed. I am going to use five different lengths of wire and in order to make sure that this is a fair test and the results are accurate, I will repeat each experiment three times and work out the average. The results will not be completely accurate as the length of wire may not be accurate. I also may not have put the voltage on the power box exactly on the right voltage. Other factors that affect the rate of reaction are Electricity. When the electricity is increased, the readings on the voltmeter and ammeter immediately change. If by accident anyone touches the knob on the power pack, the electricity given out into the circuit changes, therefore making the experiment unfair. I will work out resistance in Ohms by using Ohms Law, which is: V=IR (Voltage = Current x Resistance) The whole experiment must be as fair as possible. I will measure out the wire correctly and keep the power pack on the same voltage, in order to keep it a fair test. I will also repeat each experiment three times to make sure it is accurate. I will then draw the graph using the averages. Prediction I predict that the longer the wire is, the more resistant it will be. I. e. If the wire is 5cm, more electricity will get through the circuit than if it were a 45cm piece, at the same voltage. This is because in a long length of wire, there is more space for the electrons to move and so the more times the free electrons will collide with other free electrons. In a short length of wire, the electrons are close together and have a lower collision rate than those in a long piece of wire. This theory is backed up by Ohms law, which Apparatus Method   Collect Apparatus as shown in diagram.   Set up apparatus as shown.   Make sure power pack is set to 3v.   Measure out 15cm of wire. Clip the crocodile clips onto each end of the measured length of wire. Turn on the power pack.   Look at readings on Ammeter and Voltmeter and write down results.   Re measure and repeat two more times before moving on to next experiment.   Work out average of each experiment and use that in the graph. Safety To keep myself and others around me safe, the following should be followed: Not do this experiment near water, as people could get electrocuted. People should not touch the wire while the experiment is taking place as it could be hot and it could burn them. Girls with long hair should tie it back as they may knock something over with their hair. Results Experiment 1 Wire (cm) Readings of Ammeter Readings of Voltmeter 1Experiment 2 Wire (cm) Readings of Ammeter Readings of Voltmeter 30cmExperiment 3 Wire (cm) Readings of Ammeter Readings of Voltmeter. 17 Experiment 5 Wire (cm) Readings of Ammeter Readings of Voltmeter 75cm 0. 23 3. 23 75cm 0. 21 3. 22 75cm 0. 22 3. 23 I have worked out the averages of each experiment with a calculator to one decimal place. Here are the averages of each experiment: Wire (cm) Averages of Ammeter readings Averages of Voltmeter readings 15cm 0. 85 2. 65 30cm 0. 49 2. 96 45cm 0. 34 3. 08 60cm 0. 26 3. 16 75cm 0. 22 3. 20 Using the averages from the experiments, I have worked out the resistance of the wire. This is shown on the graph. Wire (cm) Averages of Resistance (Ohms). Conclusions My results agree with my prediction. When the length of wire is longer, there is more space for the electrons to move through the wire, therefore there is a higher chance of them colliding with each other and creating resistance. I have also seen that, through the course of the experiments, the Ammeter readings decrease, and the voltmeter readings increase. Evaluation My experiments all went well, except the Graph shows that the results are close to perfect apart from the last experiment. I noticed that through the course of the experiments, the Voltmeter readings seem to get higher in value and the Ammeter readings seem to decrease. If I had more time, I would have done the experiments more times each for a fairer test. I would also use more accurate and new equipment, as the equipment I used has been used many times before and may not measure the resistance perfectly. Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.