The Effect of Length and Thinkness of a Wire on Its Resistance

The Effect of Length and Thinkness of a Wire on Its Resistance
Aim: I am trying to investigate that how the length and thickness of a wire affects its resistance. Scientific Knowledge What is electric charge and current? Back to the everyday objects again: objects are made of molecules, molecules are made of atoms, and atoms are made of electric charges. Therefore when you look at an object, don?t imagine that it is made of little tiny atoms. Instead, imagine that it?s made of something even smaller: little tiny electric charges. Matter is made of vast quantities of electric charge, but the positive charge exactly cancels the negative. Atoms might be made of charges, but atoms are unbreakable, right? Wrong. Atoms are easily broken up. It is the nucleus of an atom which is difficult to shatter. It?s quite easy to shred atoms by pulling the negative electrons away from the tiny positive nucleus in the center of an atom. When we rubbed the balloon on our hair, we were pulling atoms apart. We should not think of atoms as if they were unbreakable little solid balls. Atoms are more like liquid droplets made of electrical charge. When atoms come together to form everyday objects, the charges which form the outside of the atoms get all mixed together.
It?s as if the world was made of charged particles, half of them being the negative electrons, and the other half being the positive cores of atoms. What would happen if we could make the electric charges flow around inside of an object? Then we would have an electric current. Now you know what an electric current really is. It?s that simple. An electric current appears whenever the negative charges in an object are forced to flow through the positive charges, or when positive charges are forced to flow through negative ones. Everyday objects are made of Electric Charge: objects are made of molecules, molecules are made of atoms, and atoms are made of positive and negative charges. Electric charge is a kind of material substance, but it is not atoms, instead it is the stuff that is inside of the atoms. If we could place equal quantities of positive charge and negative charge together, what would be the result? Neutral matter. What is A.C and D.C? The type of electricity commonly used is alternating current or AC electricity. As the name implies, the current alternates in direction as opposed to the direct current (DC) electricity that you get from batteries. The AC and DC generators are similar, but AC was proven to be a more effective way to transmit electrical power. AC is the electricity we have in our homes, and it powers our television, lights and computers. D.C DC electricity is a direct flow of electrons through a conductor such as a metal wire. A battery or DC generator usually provides a source of electrons and the potential or voltage between the positive (+) and negative (-) terminals. This flow of electrons through a wire can be thought of as similar to the constant flow of water through a hose. A.C Alternating Current or AC electricity is a back-and-forth movement of electrons in a wire, similar to sloshing water back-and-forth in a hose. When the force of a negative (-) charge is at one end of a wire and a positive (+) potential is at the other end, the electrons in the wire will move away from the (-) charge, just like in DC electricity. But if the charges at the ends of the wires are suddenly switched, the electrons will reverse their direction. The major advantage that AC electricity has over DC is that AC voltages can be transformed to higher or lower voltages. This means that the high voltages used to send electricity over great distances from the power station can be reduced to a safer voltage for use in the house. This is done by the use of a transformer. This device uses properties of AC electromagnets to change the voltages. Transformer If you make an electromagnetic by wrapping a wire around a iron rod and use AC electricity, the magnetic field will alternate at the same rate as the electric current changes. If another wire is wrapped around the rod, the changing magnetic field will create an AC current in that wire. What is especially interesting about this phenomenon is that the voltage created in the second wire depends not only on the voltage in the first wire but also on the ratio of the number of turns around the iron rod. This type of AC electromagnet with two sets of wires is called a transformer. The AC transformer is a way to easily change the voltage the electricity, something that more difficult to do with DC electricity. This invention gave AC a tremendous advantage over DC as a source of our electricity, because of the ability to easily transform voltage up or down. In electronics we are dealing with voltage, current and resistance in circuits. Voltage === Voltage is the electrical force and is a measure of the potential difference between two terminals of a battery or any component of a system. The mains have a voltage of 240v whereas battery systems use a much safer 12 or 24 volts. In the same way as height affects the flow of water, voltage affects the flow of current in a circuit. Temperature affects the voltage of a cell as the voltage goes down if it is warmer. It is measured in volts. Electrical Current ====== Current is the movement of electrical charge ? the flow of electrons other charged particles through the electronic circuit. The direction of a current is opposite to electrons flow direction. Current is measured in amperes (amps, A). Resistance == Resistance causes an opposition to the flow of electricity in a circuit. It is used to control the amount of voltage and/or amperage in a circuit. It is measured in ohms. Thermistor A temperature sensitive resistor usually made from specially processed oxides that are used to sense end of charge temperature rises and terminates high rate charging. Resistor An electrical component which restricts the amount of electricity allowed passing through it. Electrons The electrons move rapidly around the nucleus. When electrons move, free of the nuclei of atoms, and there is a net flow, this flow is called electricity, or an electric current. This might be compared to a flock of sheep moving north together, while the shepherds do not. Electric charge can be directly measured with an electrometer. Electric current can be directly measured with a galvanometer. Static electricity is not a flow of electrons at all. More correctly called a ?static charge?, it refers to a body that has more or fewer electrons than are required to balance the positive charge of the nuclei. When there is an excess of electrons, the object is said to be "negatively charged". When there are fewer electrons than protons, the object is said to be ?positively charged?. When the number of electrons and the number of protons are equal, the object is said to be electrically ?neutral?. Say, if there is a longer or thicker wire, then the number of electrons will increase, there the force of resistance will also increase. The movement of electrical charges in a conductor; carried by electrons in an electronic conductor (electronic current) or by ions in an ionic conductor (ionic current). The electrical current always flows from the positive potential end of the conductor toward the negative potential end, independent of the actual direction of motion of the differently charged current carrier particles. [image] An Atom, each shell has a maximum amount of electrons it can hold, 1st shell-2 electrons and 2nd shell ? 8 electrons. [image] Ohm?s Law Ohm?s Law says that there is a relationship between these three factors. So if you know two of the values you can easily work out the third one. V = I x R V I = V / R [image] R = V / I I X R The ?V over I and R triangle? should help you to remember these three equations. If you know the current and resistance and want to calculate the voltage, you use the first equation. If you know the voltage and resistance and want to calculate the current, you use the second equation. Lastly, if you know the voltage and current and want to calculate the resistance, you use the third equation. Symbol Circuit Component Symbol Circuit Component Switch Normally open switch Loudspeaker Loudspeaker Cell Primary or secondary cell Electric Bell Electric Bell Battery Battery of cells Diode Diode/ Rectifier Ammeter Ammeter Light Emitting Diode Light emitting diode Voltmeter Voltmeter Motor Motor Filament Lamp Filament Lamp a.c. power supply A.C. power supply Fixed Resistor Fixed Resistor Light Dependent Resistor Light dependent resistor Variable Resistor Variable Resistor Thermistor Thermistor Fuse Fuse Relay Switch Relay switch (normally open) Microphone Microphone Buzzer Buzzer Prediction: From the above knowledge, I predict that as the length of the wire increases its resistance will increase. I also believe that as the thickness increases, the resistance increases. Hypothesis: I believe this because as the length or thickness increases, so does the number of electrons that move. So there will be more resistance forcing against the electrons. There will be more resistance forcing against the free electrons. Previous Work: We repeated the test three times for the length of the wire and done the thickness of the wire three times for each thickness. Apparatus: ? Battery ? Variable Resistor ? Voltmeter ? Crocodile clips ? Different length and thickness wires ? Ammeter ? Metre ruler ? Multimeters Method: 1. I had to collect all the apparatus named above and I had to set it up as shown below. 2. Move the wire along each 10 cm and record the current and voltage reading from the multimeters, keeping in mind the thickness of the wire. 3. Repeat this test three times. 4. Measure the current and voltage on three different lengths on different thickness. Keep the lengths constant. 5. Take the results down. Safety: You should keep your hands dry because electricity conducts electricity easily through water. You have to check for un-insulated wires because they are a risk to your and others safety. Never play with the apparatus as you will be playing with electricity and could potentially get shocked. Never eat food or drink near the apparatus as this may affect it. Always check that everything is correct before turning on the power as a single mistake could be possibly fatal. Fair test: I will be using different variables in this experiment. My dependant variables are: the battery, temperature, and the apparatus. My independent variables are the length of wire and the thickness of the wire. There are a wide range of length results but there are not many thickness results. Analysis/Conclusion: I found out that as the length of wire got longer and the thickness increased, the resistance went up. This is evidence for my prediction. The graphs are sloped and are straight lines of best fits. The current graph shows that the current has a slight slope. The current decreases as the wire gets longer. There is one anolymous result on my current graph and it is on the 0.25mm thickness, at 100cm and I have circled the result. The general trend on the graph is that the thicker and shorter the wire, the higher the current. On my voltage graph all the points slope slightly upwards, they are generally parallel to each other. The graph shows the as the wire gets thicker and longer, the voltage increases. On my resistance graph the points also have a slight slope. The points slope upwards and are also generally parallel to each other. The general trend is, as the wire gets thicker and longer, the resistance increases. The lines of best fit are commonly straight. My scientific knowledge backs up my prediction by saying there are more electrons when the wire is longer and thicker. My results prove my hypothesis was correct. Evaluation: I feel I planned the experiment quite well; all the apparatus were set up as advised. The circuit was a confusing at the beginning of the experiment so I could not record results from the start of the experiment. However, once I started doing the results, I realised that they were easy. The test worked better than I had hoped because I thought I would only acquire a minute number of outcomes. I believe that my prediction was very good based on my scientific knowledge and my results table. I repeated my results three times; I did this to attain the average results table. Using this table I plotted my graphs. There were a wide range of results which helped plot the graphs. There were problems with the results though. The first problem is that resistance creates heat, and increased heat in a conductor also increases the resistance. This will therefore exaggerate results as the wire gets longer, because a longer wire has more resistance, so it will create more heat, and therefore more resistance, and therefore more heat, and so on. This is made worse by the heat conductive nature of metals due to their free electrons. The theory behind this is that when a substance increases in temperature, its atoms vibrate more. This means that the free electrons are more likely to hit a vibrating particle. If I were to repeat the experiment, it would be much easier and I might even be able to obtain more results to make my work even more accurate. I had one anolymous result, as I stated above. The cause of this result may have been to the fault of the temperature. The resistance graph should have been a straight line but they were slightly curved and they did not go through the origin. Temperature is a factor which affects the wire and this has also affected my results. If I were to do the test again I would keep in mind the room temperature so my results would become even more reliable.

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