Resistance of a wire Essay Example for Free

Resistance of a wire Essay Jack has been given a second hand D. C. dynamo and lamp. He wants to attach these to his bicycle and produce most light without blowing the bulb. What wire should he use? Variables: The variables in our investigation are The length of the wire The diameter of the wire (SWG) The type of wire Types of wire: Nichrome: 80% Nickel 20% Chromium Alloy. Constantan: 60% Copper 40% Nickel Alloy. Copper First of all we decided to test the resistance using a Multimeter. This would give us a rough idea about what the resistances of each wire are. Our lengths of wire were all 30cm long. Our results were as follows WIRE RESISTANCE ? Copper 0. 6 Nichrome 1. 2 Constantan 4. 3 Later we realised that we were using wires with completely different SWGs. To make it a fair test we needed to use wires with the same SWG. We repeated the test using a length of 30cm and an SWG of 32. Our results were as follows Our results changed dramatically. WIRE RESISTANCE ? Copper 0. 9 Nichrome 5. 8 Constantan 2. 9 Testing the current + Voltage Next we decided to test the current and voltage so that we could get a more accurate figure for the resistance. We set up a circuit consisting of, a power pack, ammeter and variable resistor in series. We also had a voltmeter in parallel to the wire we were testing. The readings we take off the ammeter and voltmeter allow us to figure out the resistance using a simple equation: Voltage ? Current = Resistance. Our circuit looked like this A variable resistor allows us to control the current going through the circuit. We needed to keep it as low as we could to avoid a heating effect in which ohms law would not take place and our results would not be accurate. Type Of Wire Current (I) Voltage (v) Display complete essay 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.