Resistance of a wire Essay Example for Free

Resistance of a wire Essay George Ohm discovered that a circuit sometimes resists the flow of electricity. He called this resistance. The rule that George Ohm came up with for working out the resistance of a wire is as followed: V/I = R V Volts I Current R Resistance This is known as Ohms Law Prediction The purpose of this experiment is to investigate the factors that affect the resistance of a wire. The hypothesis that I intent to prove or disprove is resistance will increase as the length of the wire increases, and resistance will decrease as the wire gets thicker. The experiment to come to this conclusion will be conducted as follows: firstly we attached three wires to nails that were held in place by a wooden board. The wires were attached o the nails by crocodile clips. The wires were all of different thickness, i. e. thick thin and medium circumferences. Electricity was supplied from a mains point,(in the form of volts) and from this high medium and low currents were passed through each of the wires. After all of the various currents had been passed through all of the wires, the resistance will be recorded using an ohm metre. After all of the initial measurements have been taken, the ohm metre will be moved 10 cm further away from the power supply for each of the wire, and will be further repeated in intervals of 10 cm to see if the length of the wire has any bearing on the resistance of the wire. All of the results will then be recorded in a table and then illustrated graphically to assist in the analysis of the end results. It is my prediction that as the current increases, and the length of the wire becomes longer; the resistance (measured in ohms) will increase as well. It is also my belief that as the wire gets thicker, the resistance will decrease. I also believe that the relation ship will prove to be linear and proportional between length and resistance . I devised this prediction after some careful and well thought out use of my scientific knowledge; the reasons I give for my prediction are as follows. The voltage travelling through the wires is a driving force, which effectively pushes the current around, acting as a kind of electrical pressure. A simple analogy to explain this would be to use the example of a hosepipe, i.e. a hosepipe with a greater circumference will offer less resistance than one with a smaller circumference, and also there is less surface area on a short piece of hosepipe, once again creating a smaller resistance. Also inline with my earlier analogy I believe that it will be a proportional relationship because if u double the length you double the available area for atoms within the wire The same principle can be used to explain resistance of a wire. The voltage is trying top push the current around the circuit, and the resistance is opposing it. The relative size of the voltage and resistance decide how big the current will be. So therefore if you increase the voltage, more current will flow, or more voltage will be needed to keep the same current flowing. So as a consequence I believe that a long thin wire, and the smallest will offer the greatest resistance by a thick short wire. Below is a diagram taken from the SEG physical processes revision guide (Richard Parsons 1998) that will graphically explain my above analogy. The independent variable of the wire is its length and the dependant variable of the wire is the resistance. The factors that will be kept constantly the same throughout the experiment are as followed: The thickness of the wire. The type of wire. The temperature. Safety precautions This experiment is relatively safe. The only two safety precautions that need to be taken into consideration during this experiment are: Make sure the surface you are carrying the experiment out on is dry, as a water is a conductor of electricity, and is very dangerous if they react together. Whilst the multimeter is turned on make sure you do not touch the wires, because they become very hot throughout the course of the experiment. Obtaining Firstly I attached the wire to a meter ruler with sticky tape. Then I switched the multi-meter on. The multi-meter is connection to the wire via the crocodile clips. I then recorded the resistance, lengths ranging from 0 100cm. Increasing by intervals of 10cm each time. Thick wire Low Current Medium Current High Current Length (cm) Volts (V) Ohms (R) Volts (V) Ohms (R) Volts (V) Ohms (R) Average Resistance Medium wire Low Current Medium Current High Current Length (cm) Volts (V) Ohms (R) Volts (V) Ohms (R) Volts (V) Ohms (R) Average Resistance. Thin Wire Low Current Medium Current High Current Length (cm) Volts (V) Ohms (R) Volts (V) Ohms (R) Volts (V) Ohms (R) Average Resistance Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.