What affects the resistance of a peace of wire?
...e uncontrolled because it depends on the resistance and the current. The current will be controlled but the resistance will not be controlled therefore the voltage will change. I will measure the voltage using a voltmeter. Method: 1. Get all the apparatus named above. 2. Connect the apparatus as shown in the diagram above 3. Place the connective leads with the crocodile clip on the constantan wire at 0cm and measure the results from the voltmeter and the ammeter. 4. Using the formula Ohm’s law; R=V/I. Work out the resistant using the current and voltage taken from the reading. 5. Now move the connective wire to 20cm on the constantan wire and take the readings from the voltmeter and ammeter. 6. Using the same formulae work out the resistant for 20cm. 7. Repeat this experiment for every 20cm interval till 100cm on the constantan wire. 8. Record all the data you have received. 9. Place the data in to a results graph with all the units. 10. Repeat the whole experiment again to make it a fair test. 11. Work out the average resistant for the constantan wire in the different lengths. Safety When the current flows through the wire, the wire gets hot and becomes very dangerous, therefore switch the circuit off after each testing (reading). Keep water away from the circuit as it may result in an accident. Fair Test To make my experiment fair I will have to keep some of the following variables constant. As I am testing the length, this will be changed after each reading. I will try to keep the temperature constant because if it did change then my experiment wouldn’t be fair. The cross section of the wire will also be kept the same as it can also result in a change in the reading. The type of wire I will be using will be constantan 32 gauge. I will try to keep the current constant using a Variable resistor I=V/R. The voltage and the resistance will be uncontrolled, I will measure the voltage with a voltmeter and the resistance using R=V/I. Variables Independent Dependant Controlled Length of the wire Resistance of the wire The surrounding temperature Current flowing around the circuit. Measurements In this experiments I will be measuring the current and the voltage to work out the resistance of the wire. I will measure the currents using an ammeter; the unit of measurement I will be using is Amperes A. I will measure the voltage using a voltmeter; the unit of measurement I will be using is Volts V. I will measure the resistance using Ohm’s Law: Resistance = Voltage/ Current. The unit of measurement will be Ohm . Background Scientific Knowledge of the Variables. List of factors that will affect the resistance in a piece of wire: • Length of the wire • Thickness of the wire/ cross section • Temperature • Type of wire Length- When you increase the length the resistance increases. This is because when you add more wire, you are adding more atoms, which get in the way of the electrons and slow them down. If you double the amount of electrons it in turn will mean there is more collisions. This will increase the resistance making the length and the resistance directly proportional. The wire has atoms, which are obstructive to the electrons that flow by. These particles cause a resistance as when the electrons are slowed down, the current decreases and therefore the resistance increases. Therefore, as the length of the wire increases the amount of obstructive particles increases, therefore the current will decrease in turn increasing the resistance. Temperature When the temperature increases the resistance will decrease, this is because the electrons will flow around quicker because it has more heat. They will vibrate more and move around quicker this will make the current larger; this in turn will make the resistance lower. When the temperature of a metal increases the resistance of that metal increases. This is because when the temperature increases the atoms of the metal vibrate more vigoursly because of the increase in energy. This means that the electrons have more difficulty getting through the wire as they collide with the atoms, which are in their pathway. This increases the amount of collisions therefore there is more resistance. However it is hard to keep the temperature exactly the same as the room temperature might change from day to day. It is essential to use a low voltage because it means a low current that will not heat up the wires. If a high voltage is used the energy would be in form of heat which would make the experiment unfair. The investigation will be done at room temperature. The temperature cannot be investigated because it is hard to control the range of temperature needed without the correct apparatus. Types of Wire- Different materials have different resistances because the materials' atomic structures are different so some metals have low resistances and some have high resistances. Therefore it is important to keep the material the same throughout the experiment. If different materials are used throughout the investigation, it will affect the results. Throughout the experiment Constantan and nichrome will be used. Constantan is used to make sure my conclusion works for all materials. The type of material will affect the amount of free electrons that are able to flow through the wire. The number of free electrons depends on the amount of electrons in the outer shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high number of electrons causing a lower resistance because of the increase of the number of electrons. If the particles in the material are tightly packed together, the electrons will have more collisions and therefore more resistance. Thickness of the wire- The thinner the wire the less room the electrons have to move about freely. This means that there is less current flowing as the electrons are moving slowly. This means that the current will decrease and the resistance increase. However if the wire was thicker then there will be more room for the electrons to move round and all there will be more electrons the current will then become greater and the resistance will decrease. Results Length of Wire Voltage Current Resistance Voltage Current Resistance Resistance (Average) 100 cm 2.2V 0.28A 7.86 2.2V 0.3A 7.33 7.59 80 cm 2.1V 0.35A 6 2.2V 0.36A 6.11 6.05 60 cm 2.0V 0.44A 4.55 2.1V 0.45A 4.57 4.56 40 cm 1.95V 0.61A 3.20 1.9V 0.62A 3.1 3.15 20cm 1.51V 0.90A 1.68 1.5V 1.0A 1.5 1.59 0 cm 0.00V 2.81A 0 0.1V 3.01A 0.3 0.15 Results Graph Attempt 1 Results Graph Attempt 2 Results Graph Average Graph Of All 3 Graphs Put Together Length in cm Resistance of Run 1 In Ohms Resistance of Run 2 In Ohms Resistance of Average 0 0 0.3 0.15 20 1.68 1.5 1.59 40 3.2 3.1 3.15 60 4.55 4.57 4.56 80 6 6.11 6.05 100 7.86 7.33 7.59 Analysis The Graphs for the experiment represent that they are all straight-line graphs. There is a linear relationship between the Length and the resistance. The graphs are linear proportional graphs. This is because they go straight diagonally through the origin. As it goes through the origin and it is a straight line it must mean they are directly proportional. So if you double X (Length) then Y (R...