The reading of the ammeter Essays

The reading of the ammeter Essays The reading of the ammeter Paper The reading of the ammeter Paper To find out how the length of a wire affects its resistance. Introduction- Metal is a good conductor of electricity. This is because their atoms contain small negatively charged particles called electrons. Some of these electrons are not fully attached to their atoms. This means that they can be easily detached and made to flow through the metal. This creates a current. If a wire has a low resistance, then more current will flow through the wire easily. Before the electric current was fully understood, people thought that the current flowed from the positive to the negative. This is opposite to the flow of electrons and is now know as the conventional current. An electrical current is a flow of an electric charge, so the amount of charge is will depend on the strength of the current. This is measured in Coulombs. The equation for this is: Charge= Current x Time Q = I x T Coulombs= Amperes x Seconds Factors affecting resistance Thickness- There are some factors that affect the resistance of a wire. The first of these things is the thickness of the wire. A thicker wire will have less resistance than a thin wire, because there are more paths for the electrons to flow through. The easier that it is for electrons to pass through a wire, the lower its resistance is. Material- The material a wire is made from can also have an affect on the amount of Resistance it will have. Some wires may contain more atoms than other materials. This would mean that there would be an increase in the amount of collisions between the atoms and electrons. This would mean that there might be a higher resistance. Copper would have a higher resistance than ni-crome, as the ni-crome is a better conductor of electricity that copper. Temperature- The temperature of the wire will also affect the resistance that it has. If the wire has a high temperature, then the atoms in the wire will be vibrating quickly. This will make it harder for electrons to pass through. The more heat that there is, the more resistance that there is also. Ohm investigated how the temperature of a wire can affect its resistance. Ohms law states, If the temperature of a conductor does not alter, then the current which flows through it is proportional to the potential difference applied. The gradient of this line should always be constant. You get this line by- R=I/V Resistance= Current / Voltage Ohms = Amperes / Volts. If my experiment is accurate enough and I control all the factors that affect resistance, then I should get a graph that looks a bit like this. It will have a sloping line with a constant gradient. Length- The length of a wire can also have a large affect on its resistance. A long wire will have more resistance than a short wire. This is because it is easier for electrons to pass through the short wire than through the long wire. This means that there are fewer collisions between the moving atoms in the short wire than the long wire. Therefore there is more current flowing as there is less resistance. Resistance slows down the flow of electrons through the wire. Prediction- I think that the short thick wire will have a larger current flowing through it and therefore, it will have less resistance than a long thin wire. If there is a large current, then there is a low resistance. If there is a low resistance, then there is a large current. If there are more than 6 x 10(18) electrons flowing through it per second, then the current is 1 ampere, giving a lower resistance. Preliminary work- I am going to do some preliminary work. I think that this will help me work out the best way of doing my experiment. I think that it should help me to decided which way is best to measure my results and also how often I will need to measure the wire. I am going to try and take some measurements off the three different thicknesses of wire that are available to me. I am going to use ni-crome wire of the thickness 28swg, 24swg and 22swg. I am going to keep my voltage at 4 volts, so not to burn the wire out. I am going to take the current at 10cm, 50cm and 100cm. Here are my results: Thickness (S. W. G) Length (cm) Current (amps) Resistance (ohms). Plan- Apparatus- For my experiment, I will need the following items: Three 100cm lengths of ni-crome wire.   Power pack. Ammeter.   Meter rule. Crocodile clips.   Wires.   Power supply. Diagram- Safety precautions- As an extra safety precaution, I will not use more than four volts on my wire. If I use more than four volts, then I may burn the wire out. I will also, never put the clips with ten cm of each other. This is because if I put them to close on the wire, the current flowing through them will be to strong and the wire will melt. I will also make sure that I do not touch the wire when the clips are on them. Between the clips, the wire gets very hot and if I touch it, I may burn my self on it. Fair test- To make my experiment fair, I will have to try to control certain things through the experiment. I will need to try to keep the room temperature at a constant level. This will ensure that the atoms do not gain too much energy. I will need to always keep my voltage on four, to ensure that there isnt a different amount of current flowing through the wire. I will also need to try to keep my measurements as accurate as I can. I have decided to measure the wire every two cms. I think that this will be a good amount to use as it should give me a good range of results and there wont be big gaps between them. My result table may look very big, but once I put my results on to a graph, then I should get a detailed graph of my results. I will try to use the same wire each time that I do my experiment. This is because if one wire has been used more than another, then some of the electrons may have been burned out. This would cause a decrease in the resistance. Method-The first thing that I will need to do for my experiment, is to make sure that I have all of my equipment and I have a results table ready to put my results into. Once I am ready to start, I will turn the ammeter to 20m and the voltage on the power box to 4 volts. I will then turn the power on. I will take the first wire, 28swg and place the first crocodile clip at 0cm. I will then take the second clip, and I will place it at 10cm. I will take the reading of the ammeter and write it into my results table. I will then continue to move the clip along the wire, stopping every 2cm. I will carry this on until I reach 100cm.