Aim: I am trying to find out what affect changing the length of a piece of nichrome wire has on the current flowing through it. What happens if you change the thickness as well? Diagram: I will need the following equipment: 1 x Ammeter 1 x Voltmeter 1 x Power supply 1 x Variable resistor 1 x Length of nichrome wire 1 x Meter-rule 6 x Connecting wires 1 x Crocodile clip My prediction is: If the length of the wire is increased, then the resistance will increase. This is due to the electrons having a longer distance to travel and so more collisions will occur. Due to this, the length increase should be directly proportional to the increase in resistance. Scientific knowledge: I think this will happen because, if the length doubles, then the resistance will increase in direct proportion. The reason for this is; as electrons pass through the wire, the electrons hit the positive ions of the wire whilst making the journey from one end to the other, giving opposition or resistance to the electrons.
When this happens electrons move an electromotive force such as voltage, and in hitting these positive ions, also give away their energy to these positive ions. When the wire is lengthened, the journey is longer and the resistance changes in proportion. Method: To get the results I will measure length of wire, voltage and current. The range I will use is 200 - 60 cm.
First, I set up the apparatus as above. To collect results for my graph Then I will work out the resistance using the equation R = V/I. To make it safe I will keep the current low, switch of power supply when not in use and be careful if handling live wires. To make my experiment accurate I will keep the current the same (by changing the variable resistor to keep the current the same) and by using the same thickness and type of wire. My results: Length Current 0.
3 A Current 0. 4 A Volts 'U Volts 'U Average 200 0. 75 1. 9 0. 5 1. 6 1.
75 180 0. 7 1. 8 0. 5 1. 6 1. 7 160 0.
7 1. 75 0. 5 1. 6 1.
675 140 0. 65 1. 6 0. 45 1.
5 1. 55 120 0. 6 1. 5 0.
45 1. 5 1. 5 100 0. 6 1. 5 0.
4 1. 3 1. 4 80 0. 6 1.
4 0. 4 1. 3 1. 35 60 0.
5 1. 3 0. 4 1. 3 1. 3 Evaluation: I have supported my theory that when you double the length of the wire, the resistance doubles.
I feel that my experiment went well, there were no real problems. I took my time and measured as accurately as I could, making our result satisfactory. Conclusion: Temperature If the wire is heated up, the atoms in the wire will start to vibrate more rapidly. This will cause more collisions between the electrons and the atoms, due to atoms moving into the path of the flowing electrons. This increase in collisions means that there will be an increase in resistance. Wire density If the wire has a higher density, the resistance will be higher.
This is due to the wire having more atoms in a smaller space, creating smaller and less gaps for the electrons to flow through. Because of the increased lack of space there should be more collisions. Resistance theory If the length doubles, then the resistance will increase in direct proportion. The reason for this is; 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. When this happens electrons move an electromotive force such as voltage, and in hitting these atoms, also create heat via friction of the electrons and atoms.
When the wire is lengthened, the journey is longer and the resistance changes in proportion. Current flow These electrons, positive ions (protons) make an atom of wire, positive ions are the nucleus of an atom and negative electrons revolve around the nucleus to make a sea of electrons. These electrons can be pushed out of the metal when voltage is applied causing an electricity flow.