For this investigation I looked at all the factors that could affect the results of my experiment. These are the Material of the wire. Different materials conduct in different conductivities. The better conductor the wire material is the more electric current will flow therefore the resistance will decrease. Wire Length is also another determining factor of wire conductivity, as a general rule the longer the wire is the further the current of electrons will have to travel meaning that the current will drop due to the larger amount of wire creating more resistance.
Thickness of the wire, the thicker the wire I think will add more resistance because there are more metal ions in the wire to have collisions with electrons causing more resistance in the wire. Wire temperature after the experiment has been tested/is undergoing testing. The temperature has the same detrimental effect that a thicker wire does causing more collisions and causing greater resistance to the flow of current. I will be testing overall for the resistivity of the wire over different distances of wire. AIM My aim is to investigate the resistance of a wire over set distances incrementing every 50mm.
There is little equipment needed and uses little equipment that can cause calculation errors meaning incorrect results. Also instead of testing for different thicknesses this allows me to use 1 wire and simply change the distance over which it is tested. It will also give clear and concise readings that can be trusted and used for comparing/observing trends. I chose not to measure the width of the wire and presume that the wire is of the stated thickness of 28 swg Nichrome wire. For this experiment I will assume that the wire is perfectly round at 0. 38mm diameter. FORMULA’S.
Charge is measured in coulombs and charge is the amount of current that flows every second. Electric current is measured in AMP’s (A), Charge in COULOMBS (C) 1 Volt of P. D = 1 Joule per coulomb i = Q / t Current can only flow in fully complete circles, there are two different types of circuits called parallel and series. The experiment I set up is a series circuit so that the current is either Fully ON or Fully OFF. All electrical current has energy stored as Potential energy, the voltage transferred in a circuit is measured as energy delivered by each coulomb of electricity.
This is Potential difference (P. D), potential difference is the measure of voltage difference between two points within a complete circuit. Current is recorded by using an Ammeter to find out the Amperes in a circuit, Voltmeters are used to measure P. D. I will need to use both of these to measure the Current and Voltage when carrying out my experiment. Ammeters are connected in series with the wire and the Voltmeter in parallel. Resistance of a wire relates to the amount of current able to flow. The larger the resistivity of my wire the less current will pass through.
To calculate resistance the following formula is used: R = V / I When resistance is measured the unit is given in Ohm’s. 1 ohm (? ) means 1 Volt is needed across my wire to sustain a 1Amp current, they are all related. PREDICTION Through my own knowledge gained I know that as the lengths of the wire increases so will resistivity. The electrons travelling through the wire have a larger distance to cover thus less current will pass through the wire. I predict that as the wire distance increases so will the resistivity.
If the distance tripled, I predict that so will the resistivities assuming that the wire is the same diameter all the way along and perfectly round. The resistance is directly proportional to the distance. Resistance (ohms) Length (m) PRELIMINARY TESTING Before starting the testing on my final experiment I created a small preliminary test to quickly test for trends/accuracies or potential problems that could occur. It would be easier to solve them before starting the main experiment. I tested different thicknesses of wires from 28/30/32 swg Nichrome wire thickness. I also tested the supply current wasn’t too much/too little.
This was a test to see if there were also any learning curves to overcome, this would help make the test fair before there could have been discrepancies in the final experiment. When choosing the wire I used a Micrometer to ensure that I had the correct thickness of wire and that it was reasonably accurate thickness of wire. The micrometer measures to the . 00 mm to ensure precise accuracy at very small thicknesses. During the preliminary tests we started with supply voltage on 5volts, this caused the wire of 28swg to get very hot and curl up at very high temperatures eventually snapping the wire.
Instead of using a thicker wire we chose to drop the voltage down in increments of 0. 25 Volts and decided the best voltage to use was 3volts. This supplied sufficient and reliable results and didn’t damage any of the equipment. During the test I also found that results varied due to leaving the wires to cool sometimes and testing 3 different distances back to back quickly. So in the final experiment I will leave the wire to cool for 30seconds between each change in distance. The Independent variable (I. V) will be altered using the crocodile clips to change the distance selected of the wire.
The wires will have been premeasured out to the distances 0-500mm with each increment of 50mm. Now that I have assessed how the experiment will go I am quite confident the experiment will now produce more accurate results, I will ensure this even further by repeating each test 3 times with 30seconds cool down between each test. This will be much more time consuming but will ensure that I get accurate results. I will take the average of the 3 results by adding them up and dividing by 3. In the final experiment I found that there may be an equipment error in the power pack causing +- 0.
005V fluctuations in the set voltage although this shouldn’t affect my experiment as the power pack has a dial function to set the voltage. This is quite an inaccurate way to do, so we must check the readings using a Voltmeter. APPARATUS AND SETUP Power pack – 3volts Crocodile Clips + wires 28 swg Nichrome wire Wood plank to ensure wire doesn’t burn the lab desk Meter ruler, 30cm ruler Micrometer Ammeter Voltmeter METHOD On the wooden plank, place the meter ruler and measure as accurate as possible from 0-50cm in increments of 5cm.