1) Switch on the Multimeter (which is connected to the Nichrome wire via the crocodile clips). Record the reading I get from the Multimeter and switch off the Multimeter. (This will save the battery, which will give me more accurate results. ) 2) Increase the length by 100mm until I reach 1000mm. This will give me a wide range of results to draw a graph.1) Repeat the whole experiment two more times making sure I use the same pieces of apparatus so nothing changes to make my experiment fair.
4) Take an average of the three sets of results (so that any anomalous results they will not show when I plot the averages on the graph).
5) Draw a graph and conclude the result that I have found. How I will ensure my measurements are as accurate as possible I will make sure my measurements of length are as accurate as possible by sellotaping down the Nichrome wire flat to a ruler. This will make my experiment accurate because it will ensure that I can accurately measure the length that I am going to increase it by.
The length by which I increase the crocodile clips must be accurate and precise because the investigation is about finding what affect wire length has on resistance.
How I will ensure my investigation is as fair possible 1) In my experiment I used a multimeter so the voltage in the circuit stayed the same at 9V. This means that throughout all of my experiment the voltage will be the same so that it will be fair.
2) The voltage in the circuit will stay the same and so will the current. This is because the battery, which is 9V, is controlled by the multimeter. The current is low which is good because this will not significantly heat the wire, so the results would be accurate. I will have to keep the voltage low to minimise resistance.
“This is due to kinetic theory, the more voltage, the hotter the wire, the spaces in the wire are less due to the particles moving more and there is more chance of a collision. “(1) 3) The length of the wire will go up in 100mm intervals and will be measured with a ruler so that it is accurate. For each experiment the same bit of Nichrome wire will be sellotaped to the same ruler to make sure I use the same apparatus. This will make my experiment more reliable. 4) In the circuit will be two leads with crocodile clips, a multimeter and the Nichrome wire.
I could measure the resistance of the leads and crocodile clips, and I could compensate for the resistance of the leads and clips in my results. The graphed points should give a line that goes through the origin. Where the line crosses the y-axis this gives the resistance of the leads and clips. 5) To make sure the heating effect does not affect the wire I will make sure I complete my three experiments within 15minutes on the same day. The three experiments only take 15 minutes each time to complete and if they are done at the same time they would give more accurate results than if they were done at different times.
I will also be using a thermometer to measure in degrees the temperature of the room. 6) The thickness of the wire is 0. 45mm. I can also tell this by measuring lengths of 100mm each time and testing the resistance is the same for each length of the wire I used. This is fair because if the wire were different thickness’ it would give me inaccurate results. Although the longer the length the higher the resistance, if the wire is thick its resistance is lower because its just like a resistor and works in parallel and lets the current through easily.
I think that if the wire width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions. 7) I cannot measure the temperature of the wire but the current going through the circuit is not high enough to give a significant heating affect. This will keep my experiment fair because the wire will stay the same temperature, which will not affect its resistance. I think that if the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy.
“This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. “(1) This increase in collisions means that there will be an increase in resistance. 8) The material used is Nichrome wire. This will be the same piece of wire for each experiment so it is accurate. I think that the material of the wire will affect the amount of free electrons, which are able to flow through that wire. This is because the number of electrons depends on the amount of electrons in the outer energy 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 numbers of electrons causing a lower resistance because of the increase in the number of electrons. “(1) Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase. Predictions I predict that the longer the length of the wire the higher its resistance, if the length increases then the resistance will also increase in proportion to the length. This is provided that the thickness of the wire is kept constant.
I also predict that as the cross-sectional area of the wire doubles, the resistance will half. If you subtract the resistance of the two leads and the two crocodile clips from the resistance measured during the experiment, I found that then the graph would go through the origin. Justifications The reason for my prediction is because the longer the Nichrome wire, the more atoms, which means a greater chance of electrons colliding with the atoms. The number of collisions will slow the flow of electrons down (because the electrons loose some of their energy) and increase the resistance.
“Free electrons are created, which carry a negative charge, to jump along the lines of atoms in the Nichrome wire. Resistance is when these electrons, which flow towards the positive, collide with other atoms; they transfer some of their kinetic energy. “(1) This transfer on collision is what causes resistance. “As electrons pass through the wire, the electrons hit the atoms of the wire whilst making the journey from one end to the other, giving opposition or resistance to the electrons.
“(1) When this happens it also creates heat via friction of the electrons and atoms. When the wire is lengthened, the journey is longer and the resistance changes in proportion. As the cross-sectional area of the wire doubles, the resistance will half. There would be twice as many ions and twice as many electrons bumping into them, but also twice as many electrons getting through twice as many gaps. If there are twice as many electrons getting through, there is twice the current, the resistance must have halved.
The thinner the wire is the less channels of electrons in the wire for current to flow, so the energy is not spread out as much, so the resistance will be higher: We see that if the area of the wire doubles, so does the number of possible routes for the current to flow down, therefore the energy is twice as spread out, so resistance might halve. I think the graph will be like the shape I have drawn it because I predict the longer the wire the higher the resistance and because I think the resistance of wire will go up by the same amount each time.
I think the graph will be straight in a diagonal line going to the right. The graph line does not go through the origin because even if I were to place the crocodile clips on the wire at 0mm there would still be a resistance because of the resistance of the leads. The graph would go through the origin if I took away the resistance of the leads and the crocodile clips, this would not give an accurate drawing of the graph though because when the crocodile clips are touching and connected in the circuit with the multimeter there will always be some resistance due to the leads.
Bibliography (1) = Internet resources Table of Experiment Results Length of Wire (mm) Thickness of Wire (mm) Room Temp (i?? C) Voltage (V) Current (A) Resistance of Wire (ohms) 1 Averages used to plot results Length of Wire (mm) Thickness of Wire (mm) Room Temp (i?? C) Voltage (V) Current (A) Resistance of Wire (ohms) Conclusion The longer the length of Nichrome wire, the higher the resistance.
From my graph I have shown that my prediction was correct, as the line of best fit is a straight line, this proves that the resistance of the wire is proportional to the length of the wire. The length of the wire also affects the resistance of the wire, because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion. The resistance of a wire depends on the number of collisions the electrons have with the atoms of the material, so if there is a larger number of atoms there will be a larger number of collisions, which will increase the resistance of the wire.